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Hybrid Assignment : Cart Push-Off
PHYS 153 NAME:
Hybrid Assignment: Cart Push-Off
Due Date: Thursday, March 10, 2016, at the beginning of class
You may print this sheet and write your answers on it, or write your answers on separate pages (be sure to clearly label each question
Open a web browser, and navigate to the following web page:
Look for the video called “Cart Push-Off 2.” There will be three options for using the video: DMV player (in
the browser window), or download the video and play using Quicktime, Choose an option and start the video.
You should see a frame like Figure 1 below:
Figure 1: Screenshot using DMV player
Using the video controls, you can advance the video one frame at a time. Note the scales marked on the screen for measuring position. Using the data available on-screen, answer the following questions. Where calculations are necessary, show your steps on this page or attach extra pages. We will let the positive-x direction be the forward direction of the puck (to the left on the screen). When counting frames, round to the nearest frame (e.g. 2.5 frames would be rounded up to 3 frames). We will be working with many approximations.
Play the entire video completely before you begin, then reset before you answer the following questions.
1. What is the frame rate for the video?
2. Suppose an event on the video takes 10 frames to happen. How many seconds did the event take? (Show the steps in your calculation below)
3. Consider first a system that includes both carts (and the three passengers). What is the total momentum of that system before the “push-off” happens?
4. Advance the video one frame at a time. After the push-off, how many frames does it take the front edge of Connor’s cart to travel from 0 cm to 20 cm on the right side of the screen?
5. How many seconds does it take Connor’s cart to travel that distance?
6. Calculate the average velocity of Connor’s cart after the push-off, in meters per second. We will use to the right as the positive-x direction in this video.
7. Calculate the momentum of Connor (and his cart) after the push-off. Include units, and direction.
8. After the push-off, how many frames does it take the front edge of Christine and Hailey’s cart to travel from 0 cm to 20 cm on the left side of the screen?
9. How many seconds does it take their cart to travel that distance?
10. Calculate the average velocity of Christine and Hailey’s cart after the push-off, in meters per second. Be sure to include the direction.
11. Calculate the momentum of Christine, Hailey, and their cart after the push-off. Include units, and direction.
12. How does the magnitude of Connor’s momentum compare to the magnitude of Christine & Hailey’s momentum? How do the directions compare?
13. Ideally, if we add the two momentum vectors together after the push, what should the result be? Explain your answer.
14. Calculate the percent difference between the magnitude of Connor’s momentum after the push and Christine & Hailey’s momentum after the push. (Should be less than 10%.)
15. Which cart moves faster after the push? Briefly explain why.
16. Was Connor’s momentum (alone) conserved here? Why or why not? (Use the law of conservation of momentum to justify your answer.)
17. Was the momentum of Hailey and Christine conserved here? Why or why not?
18. Was the total momentum of both carts conserved here (within a 10% difference)? Why or why not?
19. List any external forces on our two-cart system that might have affected our results.
20. The masses given in the video include uncertainties (the “plus or minus” numbers). This means that each given mass is approximate, and actually falls within a range of possible values. Consider the masses given for Connor and the cart. What are the maximum and minimum possible values for the combined mass of Connor and his cart:
Max. Possible Combined Mass:
Min. Possible Combined Mass:
1. frame rate is 240 frames per second