Class 39: Friday 1/22/2021

Warm Up:  None

Gold: 

  •  Optional test retake

Blue: Prepare for your optional test retake on Monday and friction fire on Tuesday.

Class 38: Thursday 1/21/2021

Warm Up:  None

Gold: 

  • Today: Fire from friction + marshmallow roast (hopefully!)
  • Tomorrow:  Optional test retake

Blue: Prepare for your optional test retake on Monday and friction fire on Tuesday.

Class 37: Wednesday 1/20/2021

Warm Up:  None

Today I will just be going over the tests.  To help you prepare for the retake, I will provide a video link to the solutions. 
If you have questions about the optional (extra credit) project, I can answer those.
Class 36: Tuesday 1/19/2021

Warm Up:  None -- Blue and Remote Test Today

Pick up a bearing block and/or twine if you want them
Class 35: Friday 1/15/2021

Warm Up:  None -- Gold Test Today

Project Guidelines.

Pick up a bearing block and twine if you want them

 

Class 34: Thursday 1/14/2021

Warm Up:  Draw a force diagram for each of the five numbered moments in the following scenario.  Use arrows to represent the individual and net force vectors, and name all of the forces appropriately.  Arrow lengths should be in proper proportion (approximately).

Starting from rest1, a car accelerates2 to its maximum velocity, maintains3 that velocity for a few seconds, and then brakes4 as quickly as possible, finally returning to rest5

 

  • Google Meet: 

    • Discuss the optional homework -- or anything else

    • Discuss an end of term project -- fire from friction + marshmallow roast?

  • Gold:  Test tomorrow

  • Blue and Remote: Test on Tuesday

Class 33: Wednesday 1/13/2021

Warm Up:  A 50kg rower accelerates to our left at a rate of -1m/s2. She does this by applying a 100N force to the oars.  Draw all of the forces acting on the rower and calculate their magnitudes.

 

  • Google Meet: 

    • Discuss the homework.

    • The Test:

      • Gold test this Friday.  Blue and Remote tests next Tuesday. 

      • Gold retakes next Friday (1/22).  Blue retakes on Monday, 1/25.

      • Here's the test format    pdf version

    • Practice drawing and labeling forces.

    • Discuss the "extra days" between now and the end of the term.

  • All Students -- Optional (won't be recorded) Practice: 

    • Packet p. 18-21 (More Newton's Laws in 1-D Practice) [This was another old test.]

      • This assignment has a few mistakes that you may want to fix or be aware of: 

        • The car's motion and initial acceleration in question #3 should be rightward (not leftward).

        • Problem #1 is not a great test question, but it still works.

        • Problem #5b should say "downward."

        • The coefficient of friction in problem #6 should be kinetic friction

      • Solutions

      • Video Explanations:  Part 1 (short answer), Part 1.5 (problem #1 -- a bad problem), Part 2 (problems 2-7)

Class 32: Tuesday 1/12/2021

Warm Up:  A person pushes a box with a force of 21N, as shown.  This causes the two boxes to accelerate.  If there is no friction between the boxes and their sliding surface...

1.  What is the "contact force" between the two boxes?

2.  What are all of the individual forces and net forces that are acting on each box?

3.  Compare and contrast this "contact force problem" with a "tension problem."

 

Class 31: Monday 1/11/2021

Warm Up:   Suppose a skydiver steps out of a stationary helicopter, falls until reaching terminal velocity, deploys a parachute, reaches a new terminal velocity, lands on the ground, and then stands still.  [Skydiving physics video]

Draw one force diagram for the beginning of this trip (t = 0s), another force diagram representing t = 2s,  and new force diagram for every instance when the net force switches between positive, negative, or zero.  Use labeled arrows to identify the individual and net forces, and use arrow length to show relative magnitude.

 

How many diagrams should you draw?

 

Image result for cat falling from buildingClass 30: Friday 1/8/2021

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. What's going on?

2. What's the rule for deciding whether to use "less" or "fewer?"  Which applies here?

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

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

5.  Aside from the moment of impact, when does a falling cat experience maximum net force?

 

Class 29: Thursday 1/7/2021

Warm Up: 

1. Which can you throw with more force, a Wiffle Ball® (0.045kg), a baseball (0.145kg), or a bowling ball (6.3kg)?  Or is there no difference?  Explain your thinking.

2. What limits the amount of force that you can apply when you throw a light object, like a Wiffle Ball, or a feather?

Interesting Link:  article about the fastest pitch ever thrown

 

Image result for car skidding to a stopClass 28: Wednesday 1/6/2021

Warm Up: 

If you need to stop a car quickly, why should you avoid locking the tires and skidding?

Class 27: Tuesday 1/5/2021

Warm Up:  From the homework...

15.  According to Newton’s third law, each team in a tug of war pulls with equal force on the other team. What, then, determines which team will win?

Class 26: Monday 1/4/2021

Warm Up: 

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?

 

Class 25: Tuesday 12/22/2020

Warm Up:   Santa Claus from an Engineer's Perspective

 

  • Meet: 
    • Return and discuss tests
    • Review homework
  • Homework:  Problems and Study for Retake
    • All students:  Complete Problems #10-15 from Practice with forces in 1 dimension  pdf version Answers/solutions  I recommend trying the first problem on your own and then watching the video segment for that problem.  Then try the second problem before watching that part of the video. Etc.  Here's the video
    • Blue Students:  Retakes Monday and Tuesday after break (1/4, 1/5)
    • Gold and Remote Students:  Retakes Thursday and Friday after break (1/7, 1/8)
Class 24: Monday 12/21/2020

Warm Up:  None

 

  • No Meet
  • Blue Test
  • Practice (Due before class tomorrow):

Class 23: Friday 12/18/2020

Warm Up:  None

 

  • No Meet
  • Gold Test
  • Practice (Due before class on Tuesday):

Class 22: Thursday 12/17/2020

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 next week's test, memorize this or be able to calculate it based on a known conversion.

 

Class 21: Wednesday 12/16/2020

Warm Up:    Here are the problems we made up yesterday.  Let's solve them..

1.  A projectile in free-fall travels 5m horizontally and -20m vertically, in a time of 11s.  What is its initial speed?

2.  A second projectile has an inital y velocity of 2m/s.  After 13 seconds of free-fall, it hits a horizontal surface.  At the moment of impact, its x velocity is -8.5m/s.  At what angle does the projectile hit the horizontal surface?

  • Meet
  • All Students -- Practice: None.  No homework

Class 20: Tuesday 12/15/2020

Warm Up:   

1.  What is an "asymmetric" projectile problem?

2.  How many fundamentally different types of asymmetric trajectories (for a physics problem) can you think of?

3.  What are some variables that can be incorporated into a non-symmetric projectile problem?

4.  Let's create a problem (or two).  To give time for retakes, we can solve it (them) later.

Class 19: Monday 12/14/2020

Warm Up:  

I usually solve simple (orthogonal) river problems by drawing a head-to tail diagram of the component vectors and the resultant vector.  For complicated (non-orthogonal) problems, I make a table of x and y components. 

Would a table work for simple problems, like number 1, below? 

1.  A river's current flows 5m/s southward.  A boat on the river has a velocity of 7m/s westward.  What is the boat's heading, and what is its speed relative to the water?

Here's a trickier one...

2.  A second boat, on the same river, has an eastward velocity and a northeastward heading.  Find it's speed relative to the water and its speed relative to the Earth.

 

Class 18: Friday 12/11/2020

Warm Up:  

1.  Two of the vectors A, B, and C add up to the third vector.  Which is the resultant?

2.  Point D lies on the curvy path followed by an object.  How would we properly draw the object's V, Vx, and Vy at point D?

 

Class 17: Thursday 12/10/2020

Warm Up:  Use the Range Formula to solve the homework problem that I didn't assign.

Class 16: Wednesday 12/9/2020

Warm Up:  An airplane flying horizontally with a ground speed of 120 m/s releases a bomb from a height of 4,800 meters.  If the bomb is not affected by air resistance, how far ahead of the target (in the x dimension) should the bomb be released?  Assume that the bomb is in free-fall once it is released.

 

Class 15: Tuesday, 12/8/2020

Warm Up:   Another way to identify the resultant vector...  The resultant vector in a "river problem" is the vector that is dependent on all of the other vectors.  Any one of the other vectors, if altered, would change the resultant vector.  This is not true of the component vectors.

 

Which of the following is dependent on all of the other vectors -- and is therefore the resultant vector?

--The captain of a blimp is following her compass, keeping the blimp on a Northward heading.

--A mouse, running across the running surface of a treadmill on the blimp, is traveling Eastward.

--The wind surrounding the blimp is blowing to the Southwest.

--The running surface of the treadmill is traveling Westward.

 

  • All Students -- Google Meet -
    • Return and briefly go over tests;
      • Grade Distribution --
      • Check for grading mistakes.  Instead of going over all of the details of the test in class, I have made videos explaining each question or problem.  Here are the links...
      • Blue and remote retakes will be offered next Monday and Tuesday.
      • Would the Gold people like to do their retakes this week (Thurs and Fri) or next week???
    • Discuss recent river problem assignments and talk about your progress.  Do you have questions?
  • All Students -- Practice::
    • Prepare for the test retake -- In general, each question or problem will have a comparable counterpart (testing the same concept(s)) on the retake.  For example, the problems should be solvable with the same formulas, but you may be asked for different variables, and the scenarios will be new.  The order will also vary.  The extended problem may have parts that use require formulas than the original test..
Class 14: Monday, 12/7/2020

Warm Up:  

No warm-up.  No Google Meet.  Begin the test right away.

  • Blue and Remote:
      • Test today
      • Remote students join Meet with cameras and mics on.  You will either need to print the test or answer on your own paper.
  • Homework for Everyone (unless you've already finished it): Complete #5-7 from Still More River Problems.  Check your answers and watch the video if you need extra help.
Class 13: Friday, 12/4/2020

Warm Up:  

No warm-up.  No Google Meet.  Begin the test right away.

Class 12: Thursday, 12/3/2020

Warm Up:  Get your calculators out so that you can help me with this non-orthogonal river problem...

A golf cart on an aircraft carrier is traveling with a velocity of 4m/s in a direction 32 degrees west of North, relative to the Earth.  If the aircraft carrier's velocity is 6m/s, in a direction 10 degrees east of North, what are the golf cart's heading and speedometer reading? Video of solution

  • Google Meet:
    • Discuss the homework
    • Does anyone have questions about the test?  Would any of the Blue cohort be interested in a question/answer session on Sunday at 5PM?  I could record my answers for other students.
    • Steps to solve Non-orthogonal (or orthogonal, if you want) river problems...
      1.  Identify the vectors, including the given vectors and the "unknown" vector (the one you're trying to find).
        • Identify the resultant vector (the actual velocity of "the object," relative to the Earth) . 
        • The other vectors are the component vectors that "add up" to give the resultant.
      2. Resolve all given vectors into their X and Y components.
      3. Make a three column table for adding the X and Y components of all of the vectors in the problem (including the unkown).  List the component vectors on the top rows and the resultant on the bottom row.
      4. Solve for the X and Y components of the "unknown" vector (the one you're trying to find).
      5. On a grid, draw the X and Y components of the unknown vector, head to tail.  Then draw the unknown vector itself.
      6. Use the pythagorean theorem to find the magnitude of the unkown vector.
      7. Use an inverse trig function, and your diagram, to find the direction of the unknown vector.
  • Gold Only:  Questions about tomorrow's test?
  • Blue and Remote Homework:
  • Gold Homework:
      • Study for tomorrow's test
Class 11: Wednesday, 12/2/2020

Warm Up:  

Vector A plus vector B gives the resultant vector C (vector sum).  Find the magnitude and direction of vector B.

1) Estimate the answer graphically

2) Find the answer "analytically" (by reducing these vectors to their x and y components).

ClassClass 10: Tuesday, 12/1/2020

Warm Up:  Trig Review

The figures on the right show two right triangles.  What are the magnitudes of...

1.  Arrow A?    2. Arrow B?    3.  Arrow C?    4.  Angle theta?

 

  • Google Meet:
    • Discuss the homework
    • Test format: 45 points total
      • 16 multiple choice / short answer -- 1 point each
      • 1 unit conversion -- 2 points
      • 4 Problems -- 4 points each
    • Test Schedule: (No warm-ups on these days.   Just a short bit of teaching and a short assignment.)
      • Gold Test -- Friday
      • Blue and Remote Test -- Monday
    • Begin new unit (Kinematics in 2-dimensions)
      • Unit 2 Packet (Word versionpdf version)
      • Notes: 
        • Mr. Pennington's 2-D Kinematics Notes
        • Head-to-tail Vector addition (last year's warm-up) -- the relationship between the components and resultant.  Adding vs. resolving.
  • Homework:  Complete the vector addition practice.  Here are my solutions (The solutions to 3-6 can be found on the final pages).  See Google Classroom for additional video help.
Class 9: Monday, 11/30/2020

Warm Up:  Mr. Chase suggested a way to separate motion into 9 categories, based on an object's velocity and acceleration. This categorization is based on the fact that Velocity can be +, -, or 0, and acceleration can also be +, -, or 0. 

 

Considering the motion of a swinging pendulum in the x dimension...

1.   Identify where in the video each of those 8 types of motion occurs.

2.  Which type of motion is not demonstrated?

Class 8 Friday, 11/20/2020

Warm Up:  

Sketch motion graphs for a basketball that is dropped (starting from rest) onto a gym floor and allowed to bounce back up to the point where its velocity is zero.  Create graphs for position, velocity, and acceleration vs. time. 

*For the acceleration graph, try to at least get the sign correct.

 

Class 7 Thursday, 11/19/2020

Warm Up:  I never completed Example 2, from the Class 5 notes.  Let's do it now...

Helpful hints:  1) Draw a diagram, 2) Identify "separate events" (intervals with different accelerations and/or starting points and endpoints) 3) List commonly-used variables,

  • Google Meet --
    • Discuss the first test -- would you like it to be spread out over 2 days so that we can remain mostly synchronous?  Or would you rather go asynchronous for a few days, and use a whole block for the whole test?
    • Questions about the homework?  -- Mr. Pennington's test problems
    • Discuss Extended problems -- give some tips -- draw a diagram and label some stuff
  • All Students -- Practice:  

 

Class 6 Wednesday, 11/18/2020

Warm Up:  

Sketch a graph of acceleration vs. time for a suction cup Nerf dart that is shot at a wall.  Start your graph just before the dart begins to move, and end it just after the dart stops.

Today:

Class 5 Tuesday, 11/17/2020

Warm Up:  In the physics world, an object is in "free-fall" as long as gravity is the only force acting on that object.  The object may free-fall upward or downward.  Near the Earth's surface, the acceleration of free-falling objects due to gravity is approximately -9.8m/s2

Consider this scenario...  At t = 0s, a ball is free-falling directly upward with a speed of 20m/s.  Sketch graphs of the ball's position, velocity, and acceleration (vs. time) over the next 4 seconds. [For simplicity, use g =10m/s2 instead of g = 9.8m/s2]

Today:

Class 4 Monday, 11/16/2020

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.

3.  Can you state a general rule (or some rules) for determining whether the object is speeding up or slowing down in this exercise? (i.e. speed increasing vs. speed decreasing)

Today:

 

Class 3: Friday, 11/13/2020

Warm Up:

A ball is thrown at the floor from a height of 4m.  It hits the floor and bounces back up to a height of 6m, where it is caught.  Assuming that the entire round trip takes 2 seconds…

 

1.  What is the total distance traveled by the ball on its round trip?

2.  What is the ball's displacement during this round trip? 

3.  What is the ball's average velocity for this round trip?

4.  What is the ball's average speed for this round trip?

 

Google Meet -- Use the link in Google Classroom (or watch the recording later on the class YouTube channel). Just in case I mess up today's video, here's a video of the same notes from 2017.

Homework: 

  1. Complete Graph Comparisons [p.7 & 8 of the Unit 1 Handout]    Graph Comparisons solutions  Extra Video Help
  2. Mark this assignment complete in Google Classroom!
Class 2: Thursday, 11/12/2020

Warm Up:  

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

2. Does anyone have a theory regarding why the moon is brightest on each end of the blur (in the photo from last class)?  Or did you click the link?

 

Today:

Google Meet -- Use the link in Google Classroom

Homework:

 

 

 

Class 1: Wednesday, 11/11/2020

Physics 200: Mr. Stapleton

Warm Up:  

1.  How were the photos on the right created?

2.  Suppose you attach a flashlight to a bicycle tire, as shown in the diagram.  Then you ride the bicycle in complete darkness while some one takes a long exposure photo.  What pattern will the flashlight make in the photo?  Why?

 

Today:

All Students -- 11:00 Google Meet -- Use the link in Google Classroom

  • Warm-up
  • Important things you need to know -- Highlights from the Physics 200 (Stapleton) Course Syllabus
    • Class logistics (how to find out what you're supposed to do and when you're supposed to do it)
      • Google Classroom
      • Class website
    • Grading
    • Google Classroom -- how to get credit for assignments
  • Motion matching interactive demo