Class 62 Monday-Tuesday 3/30-3/31, 2020

 

The website is back!  I'm going to be doing a hybrid Google Classroom/Website system.

Warm-Up :   

The electrophorus is charged by rubbing a cat(fur) against the top of an insulating plate (I).  Then the conducting plate (C) is placed on top of the insulating plate and is touched by the physicist.  Assuming that the cat fur has a strong affinity for negative charge...

1.  What is the charge of the plate after it is touched by the scientist? 

2.  Explain how the conducting plate becomes charged.

3.  What is the ground in this demonstration?

 

Givens for 2nd Retake (Test Version 3)

Today's Stuff (See specific completetion requirements/assignments in Google Classroom): 

 

 

Class 61.5 Friday, 3/27/20

 

I've moved into Google Classroom.  Sort of sad. :-(

 

 

Class 60 Thursday, 3/26/20

 

I've put today's stuff in Google Classroom.  Please accept your invitation.

 

 

 

Class 59.5 Wednesday, 3/25/20

 

General Information

  1.   Google Meet today at 12:40.  Here's the code: ftr-ddhv-nwm.  This link should get you there, too.

    • Questions about the test problems

    • Other questions?

      •  

 

Class 59 Tuesday, 3/24/20

 

General Information

  1.   Google Meet today from 12:05-12:45.  My tentative plan is to schedule video conferences that span what would be (if we were in school) the end of lunch and the beginning of 7/8, on A days.  We'll see how that goes and adjust if necessary.

  2.   Tests are due today.  I will grade the tests and provide videos explaining each of the problems.  For this test there will be no partial credit.  However, you only have to retake the numbers that you missed. 

    • The retake is ready to go.  I will share it with you, along with your unique values (link to values), later today.  In most cases, the retake problems represent a reversal of the original test problems.

    • Here are links to the videos explaining the test problems.  If I have graded your test, I have attempted to share them with you.  Hopefully my sharing worked.

  3.  The next unit will be Electrostatics.  I will be teaching the new unit through a series of videos that I will share with you.

 

Work to do:

  1. Once I have graded your test, watch the video(s) that explain the problem(s) that you missed -- unless you didn't miss any.  Try to solve any problems that you missed using my methods.

  2. If you have watched the video segments for the problems that you have missed, and you still have questions, check in with me for a Google Meet session tomorrow at 12:40 PM.  I'm not sure if this will work, but I have scheduled the meeting and copied this meeting ID: ftr-ddhv-nwm.   If you want to attend, try opening Google Meet at 12:40 tomorrow and pasting that ID into the "join or start a meeting" box   Hopefully, this will circumvent me needing to invite everyone.

  3. Electrostatics Work -- Complete the green highlighted steps before class time on Thursday.

    1. Here's a blank copy of the notes and practice.  Printing them is not required.  The notes cover two textbook sections.  The practice is just for section 18.1 -- Notes and Practice -- 18.1 and 18.2 (Static Electricity & Charge, Conductors and Insulators)  

    2. Filled-in version of Notes 

    3. Watch the 18.1-18.2 notes Video from last year's class -- I found it!  Sorry for the "terrifying beeping."

    4. In case you're interested, here's a link to the interesting V-Sauce episode that I mentioned at the very beginning of class (in the video from last year)

    5. Complete the Chapter 18.1 practice problems.  You don't have to turn them in.  At some point I'll have you tell me whether you completed them.  Here are the solutions... 

    6. After you finish the practice problems (or while you're finishing them), check your answers with these solutions.  It might be a good idea to also watch my short screencast -- especially for the first couple of questions, which are conceptual.

    7. In case you want a sneak preview of what last year's small test was like, here is Mr. Pennington's old test...  Electrostatics Practice Test (Mr Pennington's Old Test)  -- Answer Key

 

Class 58 Thursday, 3/19/20

 

Today: 

 

  1. If you haven't done it already, watch this video of me giving an overview of the Rotational Motion Test. Some highlights...

    • You can retake individual problems

    • Notes are allowed; you can look up formulas (including moments of inertia).

    • My intention is to make this doable enough for everyone that there's no reason to cheat.  At the same time, I think the format makes cheating more difficult; you can't just copy answers.

    • No partial credit, although wrong answers may be accepted if they represent correct calculations based on earlier wrong answers.

  2. Complete this test and share it with me before class on Tuesday.  You may use any class notes that you want, and you can look up formulas.  You're just not allowed to get help from another human being (while you're taking the test).  Share your test with me when you're ready for it to be graded or before class time on Monday, whichever comes first.  At some point I may create a Google classroom, but I haven't done it yet.

  3. Each of you will have unique values to use for every problem.  You can find your personal values on this pdf.  There were some mistakes on the first one.  This is the revised version.

  4. If you need them, here is a video with some clarifications relating to the specific problems on the test. I swear I turned my camera off, but apparently I didn't.

  5. I'm going to invite everyone to a Google Meet session on Tuesday.  I'll do it from 12:05-12:45, which, on wacky Tuesday schedule, would span the end of D-lunch and the beginning of 7/8.  Participation will not be mandatory. 

 

_____________________________________

12:06 -  Here's the fixed screencast explaining the test.  More to follow...

 

11:45 -- Please watch this screencast that I just uploaded explaining the test.  Be aware that the givens that I will be providing in PDFs will be different than those you see in the video.  This test is our first hurdle.  Don't worry; there will be retakes.  ***I just realized that some of your last names were visible in the video.  I will replace the video with one that doesn't show your names.  The link above is to my Google Drive, so hopefully that will limit other people's access until I get this replaced.  I will be adding more information here in the next half hour or so.  Mr. S.

 

 

11:28 Update... I'm going to make a screencast explaining the test format and upload it.  I may have to upload a couple, because the dirty dogs at Google decreased the time limit to 5 minutes.  At any rate, I will explain what we're going to do for the test.  I'll share the screencast with you, leave a link here, and then add links (here) to everything else you need in order to get going on the test.

Mr. S.

 

Hi Physics 200 People!  I was just in a hiring committee meeting, so I'm running a little behind.  I wanted to have everything up here by the normal start of class, but I will probably be a few minutes late.  It's 11:09 as I type this.  If there's nothing more than this, check back in a half hour or so.  Sorry for the delay!

Mr. S.

Class 57 Tuesday, 3/17/20

 

Warm Up:  No warm-up today.

Today: 

 

The highlight of today's class was this interesting (and fast) car!  Click the photo to watch the video.

 

 

 

 

 

Check you email.  I hope to start remote learning soon.

Mr. S.

 

Class 56.5 Monday, 3/16/20

 

Warm Up:  No warm-up today.

Today: 

Car project:

  • Supplies and cars are concentrated in two locations -- the cart next to the filing cabinets (glue guns in the green bag) and under the island, on the side of the room near the sink.  It's up to you to put everything back, because your physics mom had to stay home today.
  • Turn-in Predicting Rubber Band Car Velocity and Acceleration Distance.  If you're stuck on part of the calculations, just make up a value and use it to do your subsequent calculations.  
  • Make a video of your car crossing a floor tile and save the video for later confirmation (if necessary).  Email me a calculation of your top speed.  For simplicity, I will remove the distance error from scoring, so you don't have to measure acceleration distance.  Your distance prediction will still be useful in helping you video your car at the right spot.  To find your top speed, look for the moment when your rubber band releases from your car's axle (though if you no tension remains, the band may not release; your car may wind back up and stop itself).
  • You can take your cars home if you want -- either to keep them or to continue working on yours.

Rotational motion test:

  • Regarding our test, there will still be a test, but it won't be tomorrow.  The possibility of cheating is a big issue, but I think I can come up with some incentives for not cheating (like not needing to) and some roadblocks to prevent cheating.  I'll let you know when I know more, and I'll give you at least two full days notice before you have to take it.  On the other hand, in an online context, the timing might be flexible.  I'm tentatively planning on Thursday, but there may be some district ruling about when we can begin distance learning.
  • Here's the Playlist from last class.  I'm not sure if you can access it, but feel free to try.

 

Homework:

  • Stay prepared for the test (notes and practice tests).  Watch the videos if you need help.
  • Finish anything that needs finishing
  • Everything is homework, for now.
Class 56  Friday, 3/13/20

 

Warm Up:  No warm-up today.

Today: 

Coming Up:

  • Monday:  Car speed and distance measureent.

 

Homework:

  • 4 minute drill  Answers
  • Review for the test (notes and practice tests).  Watch the videos if you need help.
Class 55.5  Thursday, 3/12/20

 

Warm Up: 

1. Correction to 6d and 6f  -- please record deceleration times.

2. What's the contingency plan for this class, if school is closed?

3. Good coronavirus article for teenagers.  Important Covid-19 graph . FYI, disease name vs virus name

 

Today: 

Coming Up:

  • Friday: 4 minute drill.  Questions about test?  Finish car work.  Turn in velocity and distance prediction sheets.
  • Monday:  Car speed and distance measurement.

 

Homework:

  • Work on car calculations
  • Review for the test (notes and practice tests).  Watch the videos if you need help.
Class 55  Wednesday, 3/11/20

 

Warm Up: 

1. Derive a formula that will allow you to find the velocity of your car if you know its kinetic energy (and the wheel radii and moments of inertia).

2. How do you predict the maximum kinetic energy of a rubber band car (in order to predict maximum speed)?

 

Today: 

Coming Up:

  • Thursday:  4 minute drill.  Continue car work -- contest on Monday.
  • Friday: Test

 

Homework:

  • Review for the test (notes and practice tests).  Watch the videos if you need help.
Class 54.5  Tuesday, 3/10/20

 

Warm Up: 

1. From a physics standpoint, how does a car pop a wheelie?

2.  How can a car be designed to minimize or maximize wheelies?

 

Today: 

Coming Up:

 

Homework:

Class 54  Tuesday, 3/10/20

 

Warm Up: 

1. From a physics standpoint, how does a car pop a wheelie?

2.  How can a car be designed to minimize or maximize wheelies?

 

Today: 

Coming Up:

 

Homework:

Image result for quadcopter controlsClass 54  Monday, 3/9/20

 

Warm Up: 

A quadcopter has four propellers that usually alternate in their directions of rotation.

  1.  How does conservation of angular momentum enable this quadcopter achieve a yaw
  2.  In order to pitch or roll, why can't one motor just speed up (without the opposite motor slowing down)?

 

Today: 

Coming Up:

 

Homework:

Class 53.5  Friday, 3/6/20

 

Warm Up: 

1. What kind of rear tires do dragsters use?

2. Why do drivers do a "burnout" before each race?

3.  In what other ways do dragsters increase traction

 

Popular Mechanics Dragster Info

 

Today: 

 

Homework:

Class 53  Thursday, 3/5/20

 

Warm Up: 

1. What is the function of the steel spheres in this bearing?

2. A bearing reduces friction, but it is not frictionless.  What are the sources of friction in this bearing?  

Fun Problems:

3. If the inner ring has an outer diameter of X, and the spheres have diameters of X/2, exactly how many revolutions do the spheres make for every rotation of the inner ring (assuming that the outer ring remains motionless)? 

4.  How many revolutions do the spheres make if the outer ring makes one rotation and the inner ring stays still?

5.  What if each ring (outer and inner) makes 1 rotation, but in an opposite direction?

 

Today: 

 

Homework:

Class 52.5  Wednesday, 3/4/20

 

Warm Up: 

Suppose you need three squares of toilet paper, and one of your hands is unavailable.

1.  What strategy might you use to tear off only three squares?

2.  Why is this task easier with a nearly-full roll?

3.  The custodians at Burlington High used to remove the rolls when they were almost empty, because it became nearly impossible to pull off more than one square at a time.  Can you guess why?

 

Today: 

 

Homework:

Class 52  Friday, 2/21/20

 

Warm Up: Rubber bands are not 100% efficient.  If you do 2J of work in the process of stretching a rubber band, you won't get 2J of energy out of the rubber band when it snaps back.  Suggest a simple way to estimate the efficiency of a rubber band.

 

Today: 

 

Homework:

  • None

Class 51.5  Thursday, 2/20/20

 

Warm Up: No Warm-up

 

Today: 

  • Test retake

 

Homework:

  • Finish the rest of 19-20 Rubber Band Car Problem Set 1  Solutions

  • Check out this spreadsheet with table of car part specifications.  This should give you an idea of how much normal force will be pushing up against your wheels (and contributing to friction).  Masses do not include hot glue, rubber bands, or string -- just wood, steel, and bearings.

  • Consider a frame length for your car, and decide on wheel size.  Wheels can be scaled to any size you want, as long as they fit on the birch plywood (or as long as you make them from something that costs less than $1.)

Class 51  Wednesday, 2/19/20

 

Warm Up: Falling cats continued...

1.  Can we simulate what this cat does on a lazy Susan?

2.  We have already agreed that you can't pick yourself up by your bootstraps.  This video implies that you can turn yourself around boot straps (or maybe by a belt loop).  Is this true?

 

Today: 

 

Homework:

  • Due on Friday -- Finish the rest of 19-20 Rubber Band Car Problem Set 1  Solutions

  • Choose a frame length for your car, and decide on wheel size.  Wheels can be scaled to any size you want, as long as they fit on the birch plywood (or as long as you make them from something that costs less than $1.)

  • Tomorrow -- test retakes and work time.

  • Friday -- lay out and submit your laser cutting car design in Rhino (CAD software).

Class 50.5  Tuesday, 2/18/20

 

Warm Up: 

  1.   How do falling cats always manage to land on their feet?
  2.   Why do falling people flail their arms around?

 

Today: 

 

Homework:

  • Use your data to calculate the wheel and axle moment of inertia and friction from torque ( like #6, parts a-g)

    • Data you will need:  falling mass, fall distance (similar to thread length), acceleration time, deceleration time, axle radius

Image result for dry limbs firewood driftwoodClass 50  Monday, 2/17/20

 

Warm Up: Suppose you need to want to build a camp fire.  You have plenty of dry wood, but it's all big limbs that are too long to be manageable and too thick to break over your knee.  Without using a saw or an axe, what's the best way to divide the wood into smaller pieces?  Can you describe the proper technique?  One solution.

 

Today: 

 

Homework: Complete #1-2 in 19-20 Rubber Band Car Problem Set 1  Solutions

Class 49.5  Friday, 2/14/20

 

Warm Up: 

Explain how this jar lid closure works, in terms of Torque.

You might also consider F=kx. 

 

 

Today: 

  • Check/review homework
  • 10.5 Angular Momentum Notes and Practice -- Notes Key -- Practice Key -- Solution to #1
  • We're essentially done with new rotational material.  What next?  Options...
    • Start working on rubber band cars next week.  Finish the cars and the test after break.
    • Review and wrap things up next week.  Test on Friday before break.  Maybe start cars next week. More rubber band car work after break.

 

Homework: Complete practice problems #2-4 in 10.5 Angular Momentum Notes and Practice -- Notes Key -- Practice Key -- Solution to #1

 

 

Class 49  Wednesday, 2/13/20

 

Warm Up:  

A sphere, a cylinder, a thin hoop, and a frictionless box are released from rest at the top of ramp.  Their masses and heights are identical.

1.  Rank the objects according to their arrival times at the bottom of the ramp.

2.  Suppose the bottom end of the ramp is frictionless, and when they reach the bottom, the objects hit a vertical, frictionless wall.  What motions, if any, would continue after impact?

3.  How would the results be different if some objects had more mass or greater size than others?

4.  How would the results be different if the ramp itself were frictionless? 

 

Today: 

 

Homework: Finish all of the practice problems in Notes and Practice: Dynamics of Rotation and Rotational Kinetic Energy

 

Class 48.5  Wednesday, 2/12/20

 

Warm Up:  

1. What does a differential do?

2.  How does a differential work?

 

Today: 

 

Homework: 

Class 48  Tuesday, 2/11/20

 

Warm Up:   None

 

Today: 

 

Homework: 

Image result for compound bow drawnClass 47.5  Monday, 2/10/20

 

Warm Up:  

1.  Where does a compound bow store most of its energy?

2.  What purpose(s) do the pulleys of a compound bow serve?

 

Today: 

 

Homework: 

  • Test tomorrow over all of the notes and assignments from this unit (Momentum/Impulse/Collisions).  Part II of the test (problems) will be similar in structure to the practice test.  Part I may be multiple choice, short answer, or both.

Class 46.5  Thursday, 2/6/20

 

Warm Up:  

In the rotational (angular) motion unit, we will be using new units that are analogous to our current, linear units.  You will need to be able to work in radians.

1.  360º = _____ radians

2.  90º = _____ radians

3.  2 radians = _____ degrees

Today: 

 

Homework: 

  • Test tomorrow over all of the notes and assignments from this unit (Momentum/Impulse/Collisions).  Part II of the test (problems) will be similar in structure to the practice test.  Part I may be multiple choice, short answer, or both.

  • Due on Monday -- Angular Acceleration Practice -- Key

Class 46  Wednesday, 2/5/20

 

Warm Up:  

1.  Suppose you need to screw an abutment into a fixture that is implanted in someone's jaw.  How can you make sure that you screw it in just tight enough, but not too tight?

2.  What predictable effects (if any) does an increasing e have on collision time and collision force?

Today: 

 

Homework: 

  • Torque Practice (Pennington)   Torque Practice Solutions

  • Test on Friday over all of the notes and assignments from this unit (Momentum/Impulse/Collisions).  Part II of the test (problems) will be similar in structure to the practice test.  Part I may be multiple choice, short answer, or both.

Class 45.5  Tuesday, 2/4/20

 

Warm Up:  

Suppose some hard objects collide with one another.  Then the collision

is repeated, controlling all variables except that the collision is now cushioned. 

 

1.  In which case do the colliding objects experience a higher impulse?

    a.  When the collision is cushioned

    b.  When the collision is not cushioned

    c.   Can't tell

 

2.  In which case do the colliding objects experience a higher maximum force?

    a.  When the collision is cushioned

    b.  When the collision is not cushioned

    c.   Can't tell

 

Today: 

 

Homework: 

  • Test on Friday over all of the notes and assignments from this unit (Momentum/Impulse/Collisions).  Part II of the test (problems) will be similar in structure to the practice test.  Part I may be multiple choice, short answer, or both.

Class 45  Monday, 2/3/20

 

Warm Up:   A low-friction physics cart is release from rest.  It travels down a ramp, hits a spring, and bounces back up the hill before returning back down the hill again and continuing to bounce.  If the cart travels 0.8m on its way down the ramp (0.8m = "closing distance") and 0.6m on its way back up the ramp (0.6m = "separation distance"), what is the coefficient of restitution (e) for this collision?

 

 

Today: 

 

Homework: 

  •  Optional -- Mr. Pennington's Old Momentum Test.  Answers/Solutions.

  • Test on Friday over all of the notes and assignments from this unit (Momentum/Impulse/Collisions).  Part II of the test (problems) will be similar in structure to the practice test.  Part I may be multiple choice, short answer, or both. 

Class 44.5  Friday, 1/31/20

 

Warm Up:  

Renault Modus (compact car) vs. Volvo wagon in a head-on crash. (start at 4:30

1.  What happens?

2.  Which is safer, a car that crumples in a crash or a car that is more rigid?

3.  What questions remain after watching the video?

 

Today: 

 

Homework: 

Class 44  Thursday, 1/30/20

 

Warm Up:  

Suppose I stand a board on end and shoot it with a Nerf ® dart. 

1.  Am I more likely to knock the board over if I use a dart that sticks to the board or if I use a dart that bounces off of the board?  Why?

2.  Which experiences a greater impulse, the dart or the board?  Or do they experience the same impulse?

 

 

Today: 

 

Homework: 

Class 43.5  Wednesday, 1/29/20

 

Warm Up:  

1.  Into which end of the "potato launcher" barrel should the projectile be placed before firing?  Why?

2.  What length barrel will give the projectile the greatest speed?  [We have barrels up to 10 feet long. ]

3.  Which new concept best explains the answer to #2 -- Conservation of Momentum or Impulse?

4.  If we measure actual velocities of the projectiles, using photogates, and compare those to our predicted velocities, how do you think they will compare?

 

 

Today: 

  • Finish Ballistic pendulum activity

    • Create a spreadsheet to calculate the velocity of a projectile based on:  1) projectile mass, 2) pendulum mass, 3) pendulum swing height, in meters

    • Check your spreadsheet using the launch 1 and launch 2 data in the notes relating to ballistic pendulums.  Example

    • Create a projectile for the ballistic pendulum.  Shoot it at the pendulum, and determine its velocity.

    • Measure actual velocity using photogates

 

Homework: 

  • finish your spreadsheet.  Share it with me when you're done.

Class 43  Tuesday, 1/28/20

 

Warm Up:   A steel ball, released from rest, rolls down a ramp in the classroom.  Without using an electronic device, how might you determine the ball's speed at the end of the ramp?

 

 

Today: 

 

Homework: 

  • finish your spreadsheet.  Share it with me when you're done.

Image result for towelClass 42.5  Monday, 1/27/20

 

Warm Up:  

How can an understanding of momentum help you turn a towel into a better whip?

 

Today: 

 

Homework: 

  • None

Class 42  Friday, 1/24/20

 

Warm Up:  

1.  What will happen if I hold a tennis ball on top of a basketball and drop them to the floor together?

2.  What if I reverse their positions?

3.  Why does this happen?

 

Today: 

 

Homework: 

 

Midterm Stuff:
Review Packet   Anwers to Review Packet -- 3rd try    Last year's Midterm Study Guide
Class 41  Wednesday, 1/15/20

 

Warm Up:   Midterm discussion -- Questions?  Remember that you can't leave early.

 

Today: 

  • Optional -- test retake work time

  • Bungee Jump activity   Activity directions and data sheet

  • If you don't finish the bungee activity today, you can finish later, and I can put the grade on next semester.  It's more important that you focus on the midterm and/or your test retake.  Instead of using a real egg in a wooden enclosure, I will have you use an equivalent mass.

  • Turn in 1 bungee sheet and one graph per group.

  • Award donuts and/or gluten-free snacks -- The current leaders are Eric et. al., with a distance of 15cm.

 

Homework: 

  • Prepare for the midterm

Class 40.5  Tuesday, 1/14/20

 

Warm Up:   No warm-up today.  Get started with the egg bungee activity.

 

Today: 

 

Homework: 

  • Prepare for the midterm

  • Prepare for the bungee jump before the end of class tomorrow.  Each group must turn in one activity and sheet and one graph.

Class 40  Monday, 1/13/20

 

Warm Up:   No warm-up today.  Get started with the egg bungee activity.

 

Today: 

 

Homework: 

  • Test retake tomorrow or Wednesday.

  • If you need to finish your bungee drop tomorrow or on Wednesday, consult with your group members about test retakes.

Class 39.5  Friday, 1/10/20

 

Warm Up:   You will be dropping an egg that will be stopped by a bungee.  The force curves on the right represent force data collected from a variety of bungees.

1.  Which bungee appears to behave like a spring with a constant k?

2.  What does the area under each curve represent?

3.  If these data sets were used to calculate work done by stretching the bungee, which set(s) would cause an overestimate of work?

4.  If we used the bungee that has a well-defined k, and we estimate how far a falling egg will stretch the bungee, are we more likely to underestimate or overestimate the actual distance?  Why?

 

Today: 

  • Return tests -- retake on Tuesday or Wednesday
  • Egg Bungee Jump Activity

 

Homework: 

  • Make a spreadsheet to use in the egg bungee drop.

  • Exam review

Class 39  Thursday, 1/9/20

 

Warm Up:   None

 

Today: 

  • Test -- Work and Energy

 

Homework: 

  • Nothing required

  • Exam review

Class 38.5  Wednesday, 1/8/20

 

Warm Up:  

1.  When does each of these energy conservation equations apply to the diagram below?

2.  Would your answer change if this were a completely frictionless environment?

 

 

Today: 

 

Homework: 

  • Test on Thursday

  • No other homework

Class 38  Tuesday, 1/7/20

 

Warm Up:   A spring hangs from the ceiling.  When a mass m is attached to the end of the spring, released from that position, and allowed to come to rest, the end of the spring is a distance x lower than before the weight was added. 

 

1.  Which method below will not work for finding the spring constant k?  Why?

     Method 1:  Set the weight of the hanging mass equal to the spring force; mg = kx.  This gives us k = mg/x

     Method 2:  Assume that the gravitational PE that is lost gets converted to spring PE, so mgh = 1/2 kx2 .  Since the height lost is  

     equal to the stretch distance (x), we find that k = 2mg/x.

 

2.  Sketch a graph of PE, KE, and OE versus time.

 

Today: 

 

Homework: 

  • Test on Thursday

  • No other homework

Class 37.5  Monday, 1/6/20

 

Warm Up:  

1.  A lightweight object and a very heavy object are sliding with equal speeds along a

level frictionless surface. They both slide up the same frictionless hill.

Which rises to a greater height?

       A) The lightweight object, because it weighs less.

       B) They both slide to the same height.

       C) The heavy object, because it has greater kinetic energy.

       D) Cannot be determined from the information given.

2.  A car and a truck driving on snow with the same speed and tires with the same

coefficient of kinetic friction both lock their tires and skid to a stop.  If the truck has 2x the

mass of the car, how do their sliding distances compare?

       A) The car slides farther.

       B) The truck slides farther.

       C)  Their sliding distance is equal.

       D)  Cannot be determined from the information given.

 

Today: 

 

?? Finish Notes: Springs + Odds and Ends  Notes key  Problem solutions

 

Homework: 

Class 37  Friday, 1/3/20

 

Warm Up:  

energy skate park
Sketch graphs of mechanical PE, KE, and OE (Other energy) versus time for...

1.  Starting from rest, a child slides down a sledding hill of constant slope, reaching terminal velocity on the way.  The bottom of the hill opens to a level meadow where the child comes to rest.

 
1b.  Yesterday I gave you notes with this formula... KEi + PEi + Wnc = KEf + PEf + OEf  What is the problem with this formula, as it   
           relates to the sliding child?

2.  A dropped tennis ball bounces a few times before coming to rest.
3.  A wad of soft clay flies horizontally toward a vertical wall.  It hits the wall, falls a few meters to the floor, and comes to rest.

 

 

Today: 

  • Check/review homework:  Problems 1-3 in Notes: Springs + Odds and Ends  Notes key  Problem solutions

  • Coming up:  Work/Energy Quiz next Tuesday,  Quiz retake the following Monday or Tuesday.

  • Midterm Information (Complete Midterm Review Packet)

    • Topics/concepts will be the same as those tested by the unit tests.  While the concepts, formulas, etc. will be the same as those tested on the unit tests, do not expect any of the questions or problems to be exactly the same as those on any unit test.  As you study, make sure that you fully understand all of the concepts relating to the unit test questions and problems.  Do not just memorize answers.  To reduce your work time, some of the problems that included friction on the unit tests will not include friction on the midterm.  Be prepared to solve problems without friction.

    • Format and Distribution of Material:  100 points total --  25 Multiple choice (1 point each); 15 Problems (5 points each)

      • 1-D Kinematics:  5MC, 3 Problems

      • 2-D Kinematics: 6MC, 3 Problems

      • Newton's Laws (1-D): 6MC, 3 Problems

      • Newton's Laws (2-D): 1 Problem

      • Gravity and Circular Motion: 4MC, 3 Problems

      • Work and Energy: 4MC, 2 Problems

    • 19-20 Semester 1 Formula list  Extra points for opting out of the formula sheet (and G) -- 4%.

      Down-sized tests representing topics covered on the exam

 

Finish Notes: Springs + Odds and Ends  Notes key  Problem solutions

 

Homework:  Complete through Problem #4 in Pennington 2015-2016 test.  #7 answer is incorrect  Solutions

Class 36.5  Thursday, 1/2/20

 

Warm Up:   

Sketch graphs of mechanical PE, KE, and OE (Other energy) versus time for a yo-yo that goes down and back up (without human assistance) until it runs out of energy. [What do the steel balls and springs do?  What is the yo-yo's acceleration at the bottom?]

Today: 

Notes: Springs + Odds and Ends  Notes key  Problem solutions

 

Homework:  Problems 1-3 in Notes: Springs + Odds and Ends  Notes key  Problem solutions

Image result for wedge mechanical advantageImage result for hockey stick fulcrumImage result for boat winchClass 36  Friday, 12/20/19

 

Warm Up:   

he pictures on the right all show simple machines.  Simple machines allow the same work to be done with more convenient combinations of force and distance. 

1.  Which "machine" is fundamentally different? Why?

2.  Identify the task in each picture.

3.  For each picture, identify the machine (s).

4.  For each machine, tell how the machine alters the distance over which force must be applied by the human using the machine.

5.  How does the machine alter the force that the human must apply?

 

Today: 

 

 

Homework:  If you didn't demonstrate mastery and understanding of the Trucker's Hitch, take a rope home and practice over break.

Class 35.5  Thursday, 12/19/19

 

Warm Up:   

1.  Which planets have the fastest orbital speeds?

2.  What would we have to do in order to change the orbit of a planet? (either move it away from the sun or toward the sun)

 

Today: 

Homework:  None

Class 35  Wednesday, 12/17/19

 

Warm Up:   

None

 

Today: 

  • Test Retake

  • Work time

    • Physics homework

    • Whatever you need to do

  • Tomorrow -- check/review homework.  No new homework assigned.

  • Friday -- Machines, Trucker's Hitch, etc.

Reading (optional):

Homework: 

Class 34.5  Tuesday, 12/17/19

 

Warm Up:   

1.  Can you guess what the "sisyphus train" does?

2.  How did it get that nickname?

3.  In the context of physics energy problems, some forces are called conservative, and others are referred to as non-conservative.  Can you guess the difference between the two?

 

Today: 

Reading (optional):

Homework: 

Class 34  Monday, 12/16/19

 

Warm Up:   

Do you know how to make a cloud in a 2-liter bottle, using water and a small amount of smoke?  Can you explain it in terms of work and energy?

 

 

Today: 

Reading (optional):

Homework: 

Class 33.5 Friday, 12/13/19

 

Warm Up:   

1. How are g-forces dangerous to pilots?

2.  In this video, a driver attempts to traverse a large loop-the-loop.  In order to safely complete his mission, how many g's do you suppose the driver needs to tolerate?

 

Today: 

Reading (optional):

Homework: 

  • I didn't have time to help people with the rocket analysis during Flex yesterday, so I told them they could turn it in on Monday.  So... that option is open to everyone.
Class 33 Thursday, 12/12/19

 

Warm Up:    None.

 

Today: 

  • Test

Reading (optional):

Homework: 

  • I didn't have time to help people with the rocket analysis during Flex today, so I told them they could turn it in on Monday.  So... that option is open to everyone.
Class 32.5 Wednesday, 12/11/19

 

Warm Up:    The graphic on the right illustrates the possible scenarios for circle problems.  Sketch or visualize a scenario based on each bullet point.

 

Today: 

  • Check/review homework --   More practice-- Circular Motion, Gravitation, Kepler Solutions Solution to 16.2 --

  • Test review

    • Format -- 10-15 multiple choice over...

      • Centripetal motion

      • Law of Gravitation

      • Kepler's Laws (all 3)

    • 7 problems -- solve for some variable in the related formulas.

      • 3 Uniform Circle problems --
        • see warm-up for possibilities
        • Focus for vertical circles will be on top or bottom (not sides)
      • Law of Gravitation

      • Kepler's 3rd Law

      • Something relating to the formula for velocity of a satellite in circular orbit

      • Something relating to the formula for g.

    • Formulas:

  •  

Reading (optional):

Homework: 

  • Study -- Test tomorrow.
Class 32 Tuesday, 12/10/19

 

Warm Up:   

1.  What is a geosynchronous satellite?

2.  What's the difference between a geosynchronous orbit and a geostationary orbit?

3.  What is a space elevator?

4.  In order to manually raise an elevator, would you have to apply a force greater than the elevator's weight?  Explain.

 

Today: 

Reading (optional):

Homework: 

Class 31.5 Monday, 12/9/19

 

Warm Up:    None

 

Today: 

  • Test Retake

  • Work time

Reading (optional):

Homework: 

Class 31 Friday, 12/6/19

 

Warm Up:   

From 2016-2017 EPS 200...

The Sun, Earth, and Moon are continually spaghettifying one another.  On Earth, we see the effects of this spaghettification in the form of tides.

1.  What causes spaghettification?

2.  How much gravitational force do the Sun and Moon each exert on 1,000,000 pounds of water?

3.  Even if there were no water on Earth, there would still be tides, just as there are tides on the Moon.  Describe these tides.

4.  Why do we always see the same side of the moon?

5.  Is the Earth's 24 hour rotational period speeding up or slowing down over time? Answer

6.  Describe two ways to feel gravity.

 

Today: 

  1. Check/review homework:   #14 and 15 in Notes:  Circles, Gravity, Kepler  Solutions

  2. Kepler's 3rd Law... orbital radius and period increase together, but which one increases faster?

  3. Finish Elliptical Orbits Activity and discuss.

    • What's the easiest way to estimate the areas swept out in this orbit?

  4. Get Gravity/Circles Practice Test -- 2018-19 Test -- Solutions to 18-19 Gravity/Circles Test  (These are my solutions that I used to grade the tests; the solutions are not necessarily written so that they are easy to follow.)

Reading (optional):

Homework: 

Class 30.5 Thursday, 12/5/19

 

Warm Up:    According to the diagram on the right...

1.  At what approximate date is the Earth orbiting with the fastest speed?  When is it orbiting the slowest?

2.  Rank our seasons in order of length. Answer

 

Today: 

Reading (optional):

Homework:  .

Class 30 Wednesday, 12/4/19

 

Warm Up:  

1.  Is this an answerable question -- Approximately how fast is the jogger in this video moving?

2.  If the jogger turned around and jogged the other way, would he feel any different?

3.  What must move in order for the person to experience simulated gravity... the space station, the person, neither, or both?  What does "move" mean in outer space?

 

 

Today: 

Reading (optional):

Homework:  .

Class 29.5 Tuesday, 12/3/19

 

Warm Up:  

Consider an object tied to a string that is being swung in horizontal circles.  What forces are acting on the object?  What forces are acting on the string?

 

Today: 

Reading (optional):

Homework:  .

Class 29 Monday, 12/2/19

 

Warm Up:  

Why does tension show up so often in physics problems?  Is tension overrated?

 

Today: 

  • Test

  • Return rocket analyses

Homework:  .

  • Rocket analysis corrections (optional).  Due next Friday (12/13).
Class 28.5 Friday, 11/22/19

 

Warm Up:  

We skipped it.

 

Today: 

Homework:  .

Class 28 Thursday, 11/21/19

 

Warm Up:   None

 

Today: 

 

Homework:  .

Class 27.5 Wednesday, 11/20/19

 

Warm Up:   Are astronauts and candles weightless when they are in the international space station?  What word best sums up their motion?

 

Today: 

 

Homework:  .

  • Replacement Test Tomorrow. 

  • Get practice test tomorrow -- Newton's Laws in 2-D

Class 26.5 Monday, 11/18/19

 

Warm Up:  

A waiter is delivering a chunk of bone, basted in synovial fluid, to some dinner guests.   Touching only the serving tray (also made of bone), the waiter must deliver the dinner bone to the guests, and place it carefully on their table.  Assuming the guests' table is to our left in the picture, describe what the waiter would need to do in order to make this happen?

 

Today: 

 

Homework: 

  • Rocket analyses are due on Tomorrow.  Turn in one water rocket analysis for your group.

  • Replacement Test Day -- Next Thursday.

Class 26 Friday, 11/15/19

 

Warm Up:  

1. Cheryl wants to use some string and a nail to hang a treasured portrait of great-great-grandfather Ernesto as a young man.  The portrait is rather heavy.  Rank the three configurations on the right according to their risk of exceeding the breaking strength of the string.

2. How are static equilibrium and dynamic equilibrium different in physics problems?

 

Today: 

 

Homework: 

Class 25.5 Thursday, 11/14/19

 

Warm Up:  

A 1kg mass is suspended by a string from the ceiling of a fully-enclosed train car.  The angle shown remains constant.

1. Describe the motions of the mass and the train car in qualitative terms.

2.  How can we find the tension in the string?

3.  How can we describe the motions of the mass and the train car in quantitative terms.


Today: 

 

Homework: 

Class 25 Wednesday, 11/13/19

 

Warm Up:  

1.  One end of a rope is attached to the Gladys' belt.  Gladys is pulling directly downward on the other end. Assuming that the pulley and rope are massless and fictionless, how much downward force must Gladys apply in order to ascend?  Gladys weighs 500N.

2. This graph was created using a pressure sensor launched in a rocket during A5/6.  Why does the sensor think the rocket falls to a negative elevation at the end of its flight?

Today: 

 

Homework: 

  • Replacement Test Day -- Next Thursday.

  • Optional -- must be done alone for bonus points on the test.  Beware, no student has solved this correctly. 

Class 24 Monday, 11/11/19

 

Warm Up:     None

 

Today: 

  • Test

 

Homework: 

  • Optional -- Homerun Problem Replacement -- Find the foam ball labeled "FB."  It should be on top of the stereo receiver in C209.  Put it back when you are done measuing it.  Assume that the ball's drag coefficient is 0.47.  Suppose you want to launch this  ball at a 60 degree angle, from the school roof (height = 4m) and have it travel a horizontal distance of 15m before hitting the ground (at a height of 0m).  What initial speed must you give the ball have in order for this to work?  For extra points, determine the speed required to make it travel a horizontal distance of 30m.

Class 23.5 Friday, 11/8/19

 

Warm Up:     Suppose you're standing motionless on a motionless skateboard on level ground, and you want to travel (with the skateboard) in a direction parallel to the skateboard's length.  If you are not allowed to touch anything except the skateboard...

 

1.  Why is this a somewhat tricky task?

2.  How can you accomplish the task? 

3.  Explain the physics behind why your method works. 

 

Today: 

 

Homework: 

Study for the test.  What's on the test

  • Newton's Laws Practice Test (Last year's test)  Solutions Videos:  Multiple choice,   Short AnswerProblems 1-5Problem 6

  • Homerun Problem Replacement -- Find the foam ball labeled "FB."  It should be on top of the stereo receiver in C209.  Put it back when you are done measuing it.  Assume that the ball's drag coefficient is 0.47.  Suppose you want to launch this  ball at a 60 degree angle, from the school roof (height = 4m) and have it travel a horizontal distance of 15m before hitting the ground (at a height of 0m).  What initial speed must you give the ball have in order for this to work?  For extra points, determine the speed required to make it travel a horizontal distance of 30m.

Image result for car skidding to a stopClass 23 Thursday, 11/7/19

 

Warm Up:     If you need to stop a car quickly, why should you avoid locking the tires and skidding?  What type of friction stops a car?

 

Today: 

  • Return homerun problems.  This is a required assignment.  If you did not turn in an answer, or if you want a better score, you can solve the replacement problem, below.

  • Work on Rocket Analysis -- due on Wednesday.  If you have a group of 4, split up into 2 groups of 2 for the calculations -- and turn in two separate sheets.

  • If you think you might have the longest time aloft, write your names, time aloft, video number, and donut preferences on the board.

  • Change of plans again -- we will have a test over Newton's Laws in 1-D.  The test will be on Monday.

  • Rocket Spreadsheet for Mr. S. Use (not shared)

 

Homework: 

  • Newton's Laws Practice Test (Last year's test)  Solutions Videos:  Multiple choice,   Short AnswerProblems 1-5Problem 6

  • Homerun Problem Replacement -- Find the foam ball labeled "FB."  It should be on top of the stereo receiver in C209.  Put it back when you are done measuing it.  Assume that the ball's drag coefficient is 0.47.  Suppose you want to launch this  ball at a 60 degree angle, from the school roof (height = 4m) and have it travel a horizontal distance of 15m before hitting the ground (at a height of 0m).  What initial speed must you give the ball have in order for this to work?  For extra points, determine the speed required to make it travel a horizontal distance of 30m.

  •  

Class 22.5 Wednesday, 11/6/19

 

Warm Up:     Water rocket thrust = 2PA, where P = gauge pressure and A = nozzle cross-sectional area.

100psi = 689,500pascals = 689,500N/m2

2-Liter Bottle Neck diameter = 0.022m

Nozzle cross-sectional area (A) = pi*(0.022m/2)^2 = 3.8*10-4m2

Water Rocket Thrust = 2PA = 2 (689,500N/m2)(3.8*10-4m2) = 524N

Factoring a "Nozzle Loss Factor" of 0.16, thrust = 524N*0.84 = 440N

1.  If thrust depends solely on pressure and nozzle diameter, why does the amount of water in the rocket matter?  What is the optimal amount of water, and why is it the best?

2.  If you check your car tire pressure, and the gauge reads 40psi, what is the actual pressure in the tire?

3. Why is rocket thrust 2PA, rather than PA?  If you want a more complete explanation regarding why thrust =2PA, read this.

Today: 

 

Homework: 

  • Homerun Problem Replacement -- Find the foam ball labeled "FB."  It should be on top of the stereo receiver in C209.  Put it back when you are done measuing it.  Assume that the ball's drag coefficient is 0.47.  Suppose you want to launch this  ball at a 60 degree angle, from the school roof (height = 4m) and have it travel a horizontal distance of 30m before hitting the ground (at a height of 0m).  What initial speed must you give the ball have in order for this to work?

  • Optional -- work on problem number 11, from the rocket analysis.  This is a tricky problem.  You will probably need more space for your work than the space provided in the analysis handout margins.  Remember to change the number of bottles to 30.

Class 22 Tuesday, 11/5/19

 

Warm Up:    

1. How many 100 psi water bottles would it take to launch a human?

 

Today: 

 

Homework:  Optional -- work on problem number 11, from the rocket analysis. 

Class 21.67 Monday, 11/4/19

 

Warm Up:     None

Today: 

  • Prepare rockets for launch.

  • Turn-in homework answers.

  • Launch rockets.

 

Homework:  None

Class 21.33 Thursday, 10/31/19

 

Warm Up:    

In the diagram on the right, the tension in the rope can be found by analyzing either mass.  Rope tension = m1(g+a) = m2(g+a).  How can this be true if m2>m1?

 

Today: 

 

Homework:  Use your completed trajectory spreadsheet to find the minimum speed and optimal angle for this most efficient home run...

What is the minimum speed at which a baseball must leave a bat in order to reach the fence (in the air) 340 feet away?  What is the angle for this hit?  Assume that the density of the air is 1.22kg/m3, the mass of the baseball is 0.145kg, the circumference of the ball is 0.23m, and the ball's drag coefficient is 0.45.  You may also assume that the fence is short, with a height equal to the point of contact between the ball and the bat.  Video help

Classes 20, 20.5, 21 10/28-10/30

 

Complete all of the following before class on Thursday.

  1. Finish your projectile spreadsheet with drag.  Spreadsheet Template:  Projectile with drag   Directions Video showing how to create the spreadsheet

  2. Complete Some more practice questions/ problems. Solutions

  3. Make a rocket. 

 

Class 19.5 Friday, 10/25/19

Warm Up:    

1. How does NASA simulate weightlessness?

2. You are trying to transfer some drippy sauce across a dinner table using only a drippy spoon.  The sauce needs to go from the pot to your plate without dripping.  Touching only the spoon, how can you make this happen?

3.  What would happen if you were standing on a bathroom scale in an elevator, and the elevator suddenly began to accelerate downward at 1g?

4.  What is the source of the "butterflies in the stomach" when we fall?

 

Today: 

  • Check/discuss homework

  • What's the plan for the next three class days?

 

Homework: 

Class 19 Thursday, 10/24/19

Warm Up:    

1.  This chicken weather vane is supposed to point into the wind.  It points the wrong way.  Describe two ways to fix it.

2.  Why are hammers tricky to throw and catch?  Provide either the simple, superficial explanation or the complex explanation behind it. CM and Rotation

3.  A very light water rocket with no fins flies like a whiffle ball, but with less stablility.  It can be improved by adding fins and some weights.  Where should the fins and weights be added, and why?

Today: 

  • Check/discuss homework:  the rest of Practice Test: Newton's Laws in 1-D    Answers but not solutions  Problem Solutions

  • FINISH Notes:  3rd Law, Tension   Filled-in 3rd law notes
  • Discuss rocket construction
    • Purpose:  To investigate Newton's laws by measuring and modeling water rocket flight (including drag).
    • Goal:  Maximum time aloft for a controlled* flight.  [Controlled means vertical flight with as little lateral movement as possible -- wind permitting.  Aside from the turn-around at the zenith, there should be no rotation around any other axis than the long axis of the fuselage (i.e. fluttery flights will be disqualified).]
    • Allowed materials:  1m duct tape, 2 2-liter bottles, weights (BYOW -- batteries, rocks, coins, sand...)
    •  

      Limitations:  sole power source = 100psi compressed air, expelling tap water; no ridiculously sharp components, such as nails protruding from the nose; bottle neck must be free from interference from fins,etc., so that the rocket can be attached to the launcher; rocket must be constructed with a consideration for recyclability.

    • Primary design and operational considerations:  optimal mass, symmetry, minimal cross-sectional area, low drag coefficient, optimal water volume

    • Helpful website -- Water rocket simulator -- enter "100p" for pressure.  Then maximize performance by trying different dry masses and water volumes.

  • Start this today -- Create a new projectile spreadsheet that acknowledges the existence of air (incorporates drag).  We will be using this to analyze rockets and other projectiles flying through air.

    • Spreadsheet Template  -- make your own copy, but don't change the data in the yellow cells.  If you leave those data, you can use the screen shot below to see if your formulas are working.

    • Spreadsheet Directions -- I think there may be a mistake in here somewhere.  There was one.  Hopefully I fixed it.

    • For a screenshot of the working spreadsheet, click the thumbnail.

  • If you finish the spreadsheet, play with the water rocket simulator, above, to learn how to optimize

 

Homework: 

  • The figure on the right shows Atwood's Machine Write equations for the acceleration of the masses and the rope tension in terms of m1, m2, and/or g.  You may also assume that the rope and the pulley are both massless and that there is no friction.
Class 18.5 Wednesday, 10/23/19

Warm Up:    

1.  Consider the 3kg mass.  What does the magnitude of T2 need to be in order for the 3kg mass to accelerate upward?

2.  Consider the 2kg mass.  What relationship do T1 and T2 need to have in order for the 2kg mass to accelerate downward?

3.  Consider the string between the 2kg and 3kg masses.  What forces are acting on the string, and what conditions are necessary for the string to accelerate downward?

 

Today: 

Homework: 

Class 18 Tuesday, 10/22/19

Warm Up:    

None

 

Today: 

  • Test retake

  • Work time

Homework: 

Image result for cat falling from buildingClass 17.5 Monday, 10/21/19

Warm Up:    

According to this article, emergency clinic records of 132 cats that jumped from windows of buildings showed a 90% survival rate.  The average drop was 5.5 floors. 

Injuries increased with increasing heights up to 7 floors. When cats fell from over 7 floors, they actually suffered from “less injuries.” 

1. When does a falling cat experience zero net force?

2. When is a falling cat a "free-falling" cat?

3.  When does a falling cat experience maximum net force?

 

Today: 

Online Textbook (OpenStax) Reading: 

Homework: 

Class 17 Tuesday, 10/15/19

Warm Up:    

Is it literally possible to "pull yourself up by your own bootstraps?"  Explain.

Today: 

Online Textbook (OpenStax) Reading: 

Homework: 

Class 16.5 Monday, 10/14/19

Warm Up:    

1.  If a Wiffle® Ball has a mass of about 45g, what is the upper limit of the amount of force a thrower can apply to a Wiffle Ball during the throw?

2.  Why is there a limit to how much force can be applied to a thrown Wiffle Ball, no matter how strong the thrower is?

3.  Describe the physical characteristics of the person who could apply the most force to the Whiffle Ball by throwing it.  Who can throw a paper airplane the farthest?

 

Today: 

Online Textbook (OpenStax) Reading: 

Homework: 

Class 16 Friday, 10/11/19

Warm Up:    

1.  One way to find the center of mass (a.k.a. balance point) of a stick is to support it with two hands and then slowly move those two hands together until they meet under the stick's center of mass.  Why does this method work?

2.  Newton's 2nd Law says Fnet = ma.  Why is it okay to use this formula to calculate the force of gravity on an object that's sitting still (i.e. not accelerating)?

3.  What would the scale read, in the diagram on the right?

 

Today: 

Online Textbook (OpenStax) Reading: 

Homework: 

 

Class 15.5 Thursday, 10/10/19

Warm Up:    

What if I put a large rock on my head, with a 2"x4" on top of the rock, and then I have someone hammer a large nail through the 2"x4"?  Is this a good idea?

Today: 

Online Textbook (OpenStax) Reading: 

Homework: 

  • None :-(
Class 15 Tuesday, 10/9/19

Warm Up:    

Test today

 

Class 14.5 Tuesday, 10/8/19

Warm Up:    

It is possible to remove a sheet paper from under a dry erase pen without touching or tipping the pen.  How can one do this without tipping the pen?  Why does the pen usually fall? 

 

Today: 

Online Textbook (OpenStax) Reading: 

Homework: 

  • Study for the test.  Go through all of the homework problems.
Class 14 Monday, 10/7/19

Warm Up:    

1.  There is a heavy object suspended from the ceiling by a string.  Another segment of the same string is hanging downward from the object.  I am going to pull on the bottom string until one of the two strings breaks.  Which string is going to break first?  Why?

2.  1m/s = ____ mph.  For Wednesday's test, memorize this or be able to calculate it based on a known conversion.

 

Today: 

Online Textbook (OpenStax) Reading: 

Homework: 

  • Test on Wednesday.  Review for the test.  If you have any specific questions or topics that you would like to review, share them in class tomorrow.
  • Check your email for two optional non-orthogonal river problems
Class 13.5 Friday, 10/4/19

Warm Up:     What advice would you give next year's students, regarding preparation for this competition?  Add suggestions to this Google Doc.

 

Today: 

Homework: 

Class 13 Thursday, 10/3/19

Warm Up:    

Projectile competition

Today: 

Homework: 

  • None
Class 12.5 Wednesday, 10/2/19

Warm Up:    

In the competition you will get two shots at each target.  Suppose your first shot goes 40cm too far.  How will determine the amount of launcher adjustment that is best for your next shot? my spreadsheet

Today: 

  • Reminder -- class will be in C211 tomorrow (for the competition), not our usual C209 classroom.

  • Return launcher practice problems

  • At the end of class -- Go over the contest problems.  Do not share these with the other class before the end of today. 

  • No shooting is allowed after the handing out of the contest problems.

Homework: 

  • As a group, complete the projectile launcher contest problems.  One calibration graph should be stapled to the sheet (velocity vs. launcher setting).  This is a required grade.  You can divide the work and fill out your sheet tomorrow.  You will be using this during the contest and turning it in afterward.
  • Make sure you have a plan for dealing with angled shots, making adjustments on your 2nd shot, etc.
Class 12 Monday, 9/30/19

Warm Up:    

1.  Due to the potential destructiveness of our new projectiles, the maximum contest muzzle velocity has been reduced to 8m/s.  How can you use a horizontal launch from a stool to determine whether or not your launcher's muzzle velocity has reached this velocity? 

2.  Instead of calibrating with a horizontal launch, you might want to have one or two degrees of launch angle.  Why?

3.  Projectile contest problems may require shooting projectiles at any angle between horizontal and 70 degrees above horizontal.  How can you precisely measure, control, and maintain the angle of your projectile launcher?

4.  How can you customize your current spreadsheet to facilitate solving the launcher problems?

 

Today:  Main focus for today, Wednesday, and Thursday:  avoid damaging anything with steel balls!!!

  • Turn-in/discuss  launcher project practice problems
  • Videos for Mr. Pennington's chapter 3 test problems (plus a few requested multiple choice) are on my YouTube channel.
  • Projectile Launcher Work:
    • Never shoot a steel ball with a breakable object in your line of fire!
    • Adjust launcher power -- we discussed how to do this in the warm-up.
    • Create a calibration chart by launching horizontally from a level or near-level surface. 
      • Use a cardboard backstop with noise-reducing paper towel.
      • Record the launch height, horizontal displacement, and power setting for a range of velocities between 4m/s and 8m/s.
      • Record the launch angle, if any.
    • Create a calibration graph like this one.  Manually fit a curve to your graph.
    • Make plans for dealing with the complications arising from angled shots...
      • Launcher muzzle will be higher than the back of the muzzle, by a calculatable amount.  To account for this precisely, you need to know the length of your launcher and the position of the hole.
      • Using just your hands, it's hard to hold the launcher at a precise angle.  You may want to devise a method or a device to deal with this difficulty.
    • Set up your own test shots, and try them.

Coming Up:

  • Today -- Projectile launcher work time and homework
  • Wednesday -- Get the projectile contest problems.  Final projectile launcher work time.
  • Thursday -- Projectile contest.  To give us more space, we will be switching rooms with Mr. Yando (C211).

Homework: 

Class 11.5 Friday, 9/27/19

Warm Up:    

1.Does drag present a problem for our projectile launchers?

2. How can we answer this question?

Our spreadsheet  Spreadsheet with drag

Today:

Coming Up:

  • Friday -- review tonight's homework
  • Monday -- Projectile launcher work time and homework
  • Wednesday -- Final projectile launcher work time
  • Thursday -- Projectile contest.  To give us more space, we will be switching rooms with Mr. Yando (C211).

Homework: 

Class 11 Thursday, 9/26/19

Warm Up:    

None -- test retake day

Today:

  • Options:  test retake, work on the homework, or both.
  • If you're not retaking the test, and you want to work very quietly with other people on Mr. Pennington's test, sit at the lab tables.

Coming Up:

  • Friday -- review tonight's homework
  • Monday -- Projectile launcher work time and homework
  • Wednesday -- Final projectile launcher work time
  • Thursday -- Projectile contest.  To give us more space, we will be switching rooms with Mr. Yando (C211).

Homework: 

Class 10.5 Wednesday, 9/25/19

Warm Up:    

1.  Drawing from our growing arsenal of kinematics formulas, derive a specific formula for calculating the initial velocity (vo) of a projectile that is launched horizontally from a height (h) above the floor and which travels a horizontal distance x before landing on the floor.

2.  Given the same initial velocity, how will the range of a projectile launched at 80 degrees compare to the range of a projectile launched at 10 degrees? (assume a symmetric flight path)

 

Today:

  • Check/discuss #3 and #4 from Currents and Projectiles -- Notes and Practice Problems  Filled-in notes and solutions  Video of Notes from Class
  • A8 -- anyone who wants to see the derivations in the part of the notes that we skipped can watch the video, above, and look at the filled-in notes (also above).
  • Discuss retake -- For parts 1 and 2, each question or problem will have a similar counterpart (based on the same concept).  Part 3 will be another extended problem, but each section will not necessarily have a specific counterpart on the first test.  Please bring your first test and turn it in with your new test (so that I know how many points you originally recieved)
  • If there's time, calibrate launchers.

Homework: 

  •  None -- People who are retaking parts of the test tomorrow should study.  And don't forget to bring your old test.
Class 10 Tuesday, 9/24/19

Warm Up:    

1.  Based on the diagram to the right, provide definitions for precision and accuracy.  Which is easier to fix?

2.  What does muzzle speed mean?

3.  In our upcoming projectile contest, your launcher must be able to fire projectiles at muzzle speeds between 4m/s and 10m/s.  If your launcher has a maximum muzzle speed of 11m/s, and your friend's has a maximum muzzle speed of 20m/s, whose launcher is more precise?  Why?

4.  Suppose you want to use your spreadsheet to find the muzzle velocity of a projectile launcher.  What is the most precise method you can think of?

Today:

  • Check/discuss #1 and #2 from Currents and Projectiles -- Notes and Practice Problems  Filled-in notes and solutions  Video of Notes from Class
  • Solve the first of the launcher project practice problems
  • Begin preparing for the trajectory contest.  You will probably not get through all of this today. Calibrate your projectile launcher so that you can launch your projectile at any muzzle speed from 4m/s to 10m/s.
    1. Assemble your bands, string, and plunger.  Sand your plunger, as necessary.
    2. Get a projectile and label it with your names.
    3. If you are working in the hall, and you need to measure launch angles with your phone, take one of the green passes.
    4. Test and adjust maximum muzzle velocity.  Remember that the maximum contest velocity will be no higher than 10m/s.
    5. Develop a consistent protocol for firing, so that your shots are as precise as possible.  Ideally, you should be able to hit exactly the same spot as long as you use the same release angle, release height, and release position.
    6. Create an accurate/precise table of muzzle velocity vs. release position.  Later on, you will use these data to create a graph, and you will use that graph to shoot targets and avoid obstacles in the contest.  Directions for optional photogate method.  I'm not sure how many photogates we have.
    7. At the end of the block, remove your launcher's plunger and projectile, but leave the trigger attached to the launcher.
    8. Store your uniquely labeled projectile and your plunger assembly in the appropriate ziplock bag labeled for your class.

Homework: 

Class 9.5 Monday, 9/23/19

Warm Up:    

Use your spreadsheet to answer this question...  Suppose you launch a projectile from the top of a tall building (80m above ground level), at an upward angle of 62 degrees and with an initial velocity of 40m/s.  answers

1.  How long will the projectile remain in the air before hitting the ground?

2.  What maximum height will the projectile attain?

3.  How far, horizontally, will the projectile travel?

Today:

Homework: 

Class 9 Friday, 9/20/19

Warm Up:    

1.  The pilot of a small plane is navigating by pointing her plane directly southward while maintaining an air speed of 100m/s. If the plane has an actual eastward velocity of 50m/s, sketch a velocity vector representing the air velocity. 

To eliminate some calculations, you can describe the wind  velocity by providing its two component vectors.

2.  If there were no windshield, and the propeller were momentarily removed, would the pilot feel air blowing from straight ahead or from some other direction?

 

Today:

 

Homework: 

  •   Finish the spreadsheet described above.
Class 8.5 Thursday, 9/18/19

Warm Up:     Identify the component and resultant vectors for the following "river problems."  Then sketch them using head-to-tail vector addition.

1.  A boat travels eastward at a rate of 3m/s.  The boat's heading is northeastward, and the boat's speed in still water is 8m/s.  What is the velocity of the water in which the paddler is paddling?

2.  A quadcopter has a velocity of 20m/s westward.  The wind is blowing southward at a rate of 10m/s.  What are the quadcopter's airspeed and heading?

3.  The driver of a golf cart on an aircraft carrier uses a compass to head northward.  The cart's speedometer reads 10mph.  The aircraft carrier's heading is eastward, and it's speed in still water is15mph.  The ocean current is northwestward at a rate of 5mph.  What is the actual velocity (relative to the Earth) of the golf cart?

 

Today:

Homework: 

Class 8 Wednesday, 9/18/19

Warm Up:   

 No warm-up.  Test day

 

Today:

  • Test

Homework: 

Class 7.5 Tuesday, 9/17/19

Warm Up:   

 Two canoe paddlers begin at the starting point in the diagram on the right.  They paddle with a constant water speed.  Paddler A keeps the canoe pointed westward while paddler B keeps the canoe pointed at the small island.

1.  What do you think is the difference between water speed and speed?

2.  Which paddler is following a heading?

3.  Describe the shape of the path followed by each paddler.

4.  Now suppose we increase the scale of the problem, and we remove the current.  Paddler A again gets a compass, but only at the beginning of her journey.  She points her canoe westward, begins traveling in that direction, and maintains her speed in a perfectly straight path (except for curving around the Earth).  Assuming that her path is perfectly straight, why will she end up South of the island, regardless of her hemisphere?

 

Today:

  • Check/review "Classic River Problem," from Combined handout with notes, analytic vector practice, and river problems
  • Questions relating to the test? 
    • For the practical problem, a timer and a meter stick will be provided.  Make sure that you can measure in meters, using a meter stick.
    • Test topics include all of the notes, homework, and practice tests before class #7.  It wouldn't hurt to review some of the warm-ups, as well.

Homework: 

  • Due on Thursday -- complete the rest of the "Analytic Addition of Non-Orthogonal Vectors Drill" in the recent handout. Non-Orthogonal Vectors (Solutions).  Watch my recent YouTube video if you need help.
Class 7 Monday, 9/15/19

Warm Up:   

1.  Suppose the two vectors on the right represent two forces acting on the clam.  In what direction will the clam accelerate?  What will be the magnitude of the net force accelerating the clam in that direction?

2.  The diagram on the right shows a top view of a train car that is moving at a rate of 2m/s.  You are in the car.  In which direction and how fast should you walk in order to have the intended velocity shown on the right.

3.  Sketch acceleration graphs for these events... my answers

a.  A pitcher throws a fastball to a batter, and the batter hits a line drive that is caught by the pitcher.  Sketch a graph of the ball's acceleration, assuming the pitch is moving forward.

b. A large, air-filled latex balloon is dropped from a height of 20 feet.  The balloon hits a tile floor, bounces upward, and stops at some maximum height.

c.  A pedestrian is walking to our right at a constant pace.  As she does this, she swings her arms normally.  Graph the horizontal acceleration of her right hand, beginning at the moment her left foot touches the ground and ending three steps later.

 

Today:

Homework: 

Class 6.5 Friday, 9/13/19

Warm Up:   List all of the kinematics formulas that we have been using

1. vave =

2. vave =

3. vfinal =

4. a =

5. displacement =

6. (vfinal)2 =

 

Today:

Homework: 

Class 6 Thursday, 9/12/19

Warm Up: 

1.  What kinematic information can we get by calculaing the area "under" the curve of a velocity vs. time graph?

2.  What does the area under the curve of an acceleration vs. time graph tell us?

3.  Does the area under the curve of a position graph tell us anything?

4.  Suppose we graph the acceleration of a blowgun dart that is shot across the room, sticking to the opposite wall.  How can #2, above, help us draw that graph?

 

Today:

  • Finish reviewing homework  --  Extended Kinematics Problems Answer Key
  • A7/8 -- Discuss sliding block solutions  My sliding block video  My solution
    • On a test, if you want partial credit, make sure you clearly write the original formula(s) that you are using.
  • Questions about unit conversion practice?
  • Practical Problem
    • Use the materials provided in the room, to find the sphere's acceleration on each slope, and it's maximum speed.  The sphere will probably fall off when you roll it, so here's a Link to a video that you can use to finish this.

Homework: 

  • Practice Test #2  Solutions except for conceptual #5 and problem #5 solutions to #5 and #5
  • Replace a missing homework with 100% if you answer this correctly on your own and show your work...  Suppose you run a two lap race.  How much faster must your second lap be, compared to your first, if you want your average speed for the entire race to be twice the average speed of your first lap?  Your answer can be in the form of a multiple (e.g. 2x faster, 3x faster, etc.)
Class 5.5 Wednesday, 9/11/19

Warm Up: 

What would the graphs look like if you graphed acceleration for these events? My answers

1.  A PE student runs from one end of the gym to the other and back (wall to wall) as fast as possible.

2.  A basketball is dropped from high above a gym floor and bounces back up until its velocity reaches zero.

3.  A skydiver steps out of a plane, begins to fall, opens a parachute, falls some more, and hits the ground.  [Assume all motion is vertical.]

 

Today:

Homework:  Finish the extended problems, if you haven't already finished them.

Class 5 Tuesday, 9/10/19

Warm Up: 

1.  A race car is traveling counterclockwise around a circular track.  The car's speedometer stays on exactly 100mph the whole time.

Describe what happens to each of the following as the car makes one revolution around the track:  

a)  the car's speed   b) the car's velocity  c) the car's acceleration.

2.  How would you use dimensional analysis to convert 4m/s to mph?  Mathematically speaking, why does dimensional analysis work?

 

Today:

Homework:

Class 4.5 Monday, 9/9/19

Warm Up: 

Match each position vs. time graph with the correct velocity and acceleration graph.

Today:

  • Check/review homework.  Discuss the acceleration graph.  Why does it look terrible?  What should it really look like?  What's going on at different points in time?  Stapleton graphs
  • Alone or in pairs (one group of three is allowed, per class), find an answer to the sliding block question that follows...
    •  Theoretically, the coefficient of kinetic friction between two surfaces allows us to calculate the force of friction between two surfaces that are sliding past one another.  For an object freely sliding across a horizontal surface, .  Therefore, using Newton's 2nd Law, it can be shown that the coefficient of friction = -a/g.  Find the coefficient of friction between a wooden block and the tile floor.  Briefly explain your methods and show your work.

Homework:

Class 4 Friday, 9/6/19

Warm Up: 

A ball is launched directly upward from the Earth's surface.  The ball returns to Earth and hits the ground after a time of 10 seconds.  Assuming no air resistance and g≈10m/s2, fill in the values in the diagram on the right. [Though the diagram appears to show horizontal motion, assume that there is none.]

Today:

Homework:

  • Create Motion Graphs using Google Sheets:
    • Mr. Stapleton collected floor tile and video frame number data from this video. Use those data (in this Google Sheets template) to create graphs of position vs. time, velocity vs. time, and acceleration vs. time.  You will need to make your own copy of the spreadsheet first.  Rename it with your name. 
    • What to turn in:
      1. Print out the acceleration vs. time graph and add notes to the graph explaining what the spool tractor is doing at various times and how that relates to the points on the acceleration graph.  For example, start with a note pointing to the positive dots at the beginning, and the fact that they indicate that the car is moving forward and speeding up.
      2. Propose an explanation for why the acceleration graph looks so bad [The answer is not that Mr. Stapleton was sloppy and careless!].
      3. Share the spreadsheet with jstapleton@ewsd.org.
    • What to do if you're stuck -- Videos showing how to create the spreadsheet (I get better in each video) :  Part 1, Part 2, Part 3
Class 3.5 Thursday, 9/5/19

Warm Up: 

The symbol "g" usually represents the absolute value of the acceleration of gravity near Earth's surface (in the absence of air resistance).  The approximate value of g is 9.8m/s2, but the acceleration of objects due to gravity is -9.8m/s2.

 

For simplicity, use g = 10m/s2 to complete these motion graphs for an object with v0 = 20m/s and y0 = 0m.

[Ignore air resistance.]

Today:

  • Check completion of homework -- quickly go over answers.  If you have questions, watch one of these videos of me explaining the problems from last night's homework (#1-6, #7)  If you still have questions, ask them tomorrow.
  • Get your spool tractors tested, ASAP.
  • Spool tractor prediction and selection form -- add your preferred Dunkin donut styles/flavors to the form.

Homework:

Class 3 Wednesday, 9/4/19

Warm Up: 

1. For letter a, on the right describe what an object could be doing in order to have both positive velocity and positive acceleration.

2.  Do the same for the rest of the letters.

Today:

Homework:

Class 2.5 Tuesday, 9/3/19

Warm Up:

1.  Assuming that the man in the picture is 2m tall, and the frame rate of the camera was the usual 30 frames per second, what were the approximate maximum and minimum speeds of the object?

2.  Based on your answers, do you think the assumption of 30 frames per second was too low, too high, or about right?

Today:

Homework:

  • None
Class 2 Friday, 8/30/19

Warm Up:

Use the velocity vs time graph on the right to sketch the shape of a corresponding position vs time graph.

[Hint: positive velocity corresponds to movement away from a motion sensor.]

Today:

  • Get the free app, Coach My Video
  • Turn-in signed course expectations
  • Check/review homework
  • Finish reviewing courses expectations.
  • Complete Acceleration Notes -- Answer Key
  • Spool tractor challenge -- try to build a spool tractor today; practice on Tuesday; contest on Wednesday.

Handouts:

Homework:

Class 1.5 Thursday, 8/29/19

Warm Up:

For each letter, describe what is happening to the person's speed and direction during the 10 seconds represented on the graph.  

Today:

\Online Textbook Reading:

Homework:

Class 1: Wednesday, 8/28/19

Physics 200: Mr. Stapleton

Warm Up:

Spin one of the "sprotating cylinders" by pressing one end until it squirts out from under your finger.  Try pressing the other end.

When the cylinder is spinning, why do you only see the symbol that you press?

Slow motion

Today:

  • ___ students log in to desktops ASAP 
  • Learn names/pronunciations
  • Enter attendance
  • Student info sheet
  • Check to see if you're on my email list, find my website, and see if your chromebook is working in here.
  • Preview
    • of the year (see last year's site).
    • This unit -- check out the practice tests from last year's class 6.
  • Briefly go over course expectations (grading, homework, talking, clean-up)
  • About Me (mostly)
  • Motion Matching Activity
  • ***A5/6 has D lunch (12:40)  --
  • B-Day Split block times (I think) are:
    • B5 -- 1150-12:28
    • B6 -- 12:32-1:10

Handouts:

Online Textbook Reading:

Homework: