Class 13: Thursday, 3/12

Warm Up: 

1.  Solve this simple problem... a 100% efficient 1kg robot uses its motor to accelerate from rest across level ground.  If the motor uses 0.5J of energy during this process, what is the robot's final speed?

 

2.  Does the entire 0.5J of energy get transferred to the robot, or does some of it also go to the Earth?  Do we need to recalculate the robot's speed to account for the energy that is transferred to the Earth?

 

Today:

Homework:  

  •  
Class 12: Tuesday, 3/10

Warm Up:  None

 

Today:

  • Test retake: circular motion, gravity,

Homework:  

 
Class 11: Friday, 3/6

Warm Up:  Suppose I place some foam on my table top, and then I shoot it with the two darts in the picture, using the same Nerf ® gun.  Compare the effects of the two darts impact on the motion of the foam.

Today:

  • Check/review homework
  • Finish the notes (#16 on p.3)
  • Choose Rubber Band Car Groups -- so that I can gather sufficient materials
  • Questions about the circles and energy test retake?
  • Other stuff?
    • Force plate
      • Bouncing
      • Jumping
      • Dropping
    • Gauss Gun
    • Newton's Cradle -- how it works (partly)
  • Start Momentum and Impulse practice test

Homework:  

  • Test retake next Tuesday
  • P. 7-8 (practice test) due next Thursday Momentum and Impulse Handout (pdf)  Handout Key -- The multiple choice questions are probably trickier than the questions on the real test.
  • Optional:  there are more practice problems in the handout that I don't plan to assign for homework.  Try them if you want more practice.

 
Class 10: Wednesday, 3/4

Warm Up: 

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

2.  The momentum formula is p = mv  (momentum is "p").  Can you explain the balls' behavior in terms of the momentum formula?

3.  How could this concept be applied to towel snapping?

Today:

Homework:  

  •  Problems 1-3, 10, and 13 on p. 4-6.  Handout Key
  • Test retake next Tuesday
    • If you want more roller coaster problem practice, watch this video.  Then print out a fresh copy of page 8 from the last handout.

 
Class 10: Thursday, 2/19

Warm Up: 

There is a "pith ball" hanging next to the Van de Graaff generator.  The pith ball is foam that is covered with a conductive, metallic paint.  What do you think will happen when the Van de Graaff generator builds up a strong negative charge?  Why?

Today:

Homework:  

  •  Have a great break!
Class 9: Tuesday, 2/17

Warm Up: 

Today:

  • Test

Homework:  

  • None
Image result for compound bow drawnClass 8: Friday, 2/13

Warm Up: 

How and why does a compound bow change the nature of W=Fd?

Today:

  • Check/review homework
  • Test review (test on Tuesday)
  • If there's time -- start some static electricity demos

Homework:  

  •  Test prep
Class 7: Wednesday, 2/11

Warm Up:  None

Today:

  • Try out the sled park feature
  • Work time

Homework:  

  •  Continue practice test
Class 6: Monday, 2/9

Warm Up: 

1.  What is the point of having a variety of gears on a bicycle? (or a car, motorcycle, etc.)

2.  If you ride as fast as possible in one gear, how does your acceleration change over time?

3.  How does changing to a higher gear affect the F and d components of your work (e.g. Fd vs Fd)?   Consider changes to F and d where your foot meets the pedal and where the tire meets the road.

4.  At what point should you change gears?

Today:

Homework:  

  •  Practice Test -- due on Friday  Answers
  • Test on Tuesday
Class 5: Thursday, 2/5

Warm Up: 

In this video, a driver supposedly enters a loop-the-loop at a speed of 36mph (16.1m/s).  The driver supposedly experiences 6g at the bottom and approximately 0g at the top.  They say the loop is 40feet high, so the radius is approximately 6.1m. 

1.  In all of the practice problems we have done so far, how many more gs are experienced at the bottom of a loop-the-loop, compared to the top?

2.  Why isn't that the case here?

3.  Does the driver really experience 6g at the bottom, or is it closer to 5g?

*This would be a good context for a bonus problem.

Today:

  • Check/review homework
  • The real sled launch will be next Wednesday.  Tuesday was just data collection, so we can figure out how to do next Wednesday safely.  Bring warm stuff again.
  • Work on the roller coaster problem

Homework:  

  • At least #1 and #2 (and #3 if you want a little more practice) of the Sledding Energy Problems (pdf)  Solutions
  • Optional -- think about how we should design a jump to give everyone a comfortable landing.  We have some control over speed, but not super-precise control.  The current dimensions of the snow pile that we have to work with are (very roughly) about 15m long x 3m wide x 1m high.  I made this spreadsheet to let you easily visualize the flight paths of 3 jumpers.  You can make a copy and adjust the values.  I haven't reviewed all of the video from Tuesday, but our velocities ranged from about 18mph to 35mph.
Class 4: Tuesday, 2/3

Warm Up: 

We're going to use the law of conservation of energy to find out how many pullers it takes to accelerate the sled to a target speed -- for any occupant mass.

 

1) What does this equation look like for the 15m (approximately) over which the sled accelerates?

2) How are we going to use this equation to find the number of pullers required to accelerate the sled to a target velocity?

3) What data do we need to collect?

Today:

  • Check/review homework
  • Sled Accelerator Data Collection -- there's a google spreadsheet in Classroom.
  • Homework work time

Homework:  

  •  P.10-11 (#1-4)
Class 3: Friday, 1/30

Warm Up: 

1.  Why do we have tides?

2.  Why is there a high tide on the opposite side of the Earth from the Moon?

3. Which object is excerting a greater gravitational force on you right now, the Moon or the Sun?

4.  How are tides related to black holes and spaghettification?

 

Today:

Homework:  

Class 2: Wednesday, 1/28

Warm Up: 

We don't have to answer all of these.

1.  What is the net force acting on the jogger in the video?  What is exerting this force?

2.  Approximately how fast is the jogger in this video moving?

3.  If the jogger turned around and jogged the other way, would he feel any different?  What if he ran faster? 

4.  What if the floor didn't have any friction (and no drag in the air)?

5.  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?

6.  There are essentially two ways to simulate 1g of gravity in "outer space."  What are they?  How are they similar?  How are they different?  How do they compare to real gravity?

 

Today:

  • Check/Review Homework
  • Newton's Law of Gravitation -- and practice problems.  Video is on the class playlist.
  • Sled accelorator data collection on Tuesday (Friday is too cold and too soon).  Wear warm clothes and footwear with good traction.  Bring a helmet if you want to wear yours.

Homework:  

  • Four Problems
    • P.6, #16
    • P.7, #3
    • P.8, #4
Class 1: Thursday, 1/22

Warm Up:  What's happening to this guy?  Why? 

Today:

  • Return exams
  • Are there any more completed course recommendation sheets out there?
  • Mid-Year Mop-Up -- tentative plan --  2 classes each of: centripetal motion/gravity, energy/work, momentum/impulse.  Then a practice test and a test.
  • This new unit is interesting, but it doesn't have to be hard.  There are just three new things... 1) Net force = mv2/r   2) Net force is centripetal   3) We have a new way to calculate weight/Fgravity
  • Unit 4 Handout:  Centripetal Acceleration and Gravity (PDF)  Answer Key
  • Derivation of ac = v2/r (direction and magnitude)
  • Work through Handout:  VIDEO of today's notes
    • Change the name of the handout to "Unit 4."
    • Get rid of the last part of the problem on the first problem #4 (p.3)
    • Work on practice problems 1, 2, and 4, on p. 3-4.

Homework:  

  • 3 problems on 2 different pages:
    • Page 3, #3 and #5

Link to 1st Semester