Extra Credit 7

Impulse and momentum

In this exercise you will analyze two video clips,  impulse_1.mp4 and the impulse_2.mp4.  The clips show a cart being pulled by a constant force F for some time interval ∆t.  The velocity of the cart at t = 0 is zero.   After the time interval the force is zero and the cart moves with approximately constant velocity.   You will determine the magnitude of the impulse I = F∆t received by the cart, and its velocity and momentum after the force has dropped to zero.


In the video clip impulse_1.mp4 the cart is pulled by a constant force for some time ∆t.  If you bring up the clip and use the step up button, you will see that the force sensor reading varies between 0.76 and 0.72 N until you get to approximately 1.4 seconds.  (The time box displays the time for each frame.)   At ∆t  ~1.4 s the force sensor reading drops to ~0.

During the first 1.4 s, when the force is not zero, the cart is accelerating.  Its velocity and therefore its momentum are changing.  The impulse F*∆t  is equal to the change in momentum ∆p = pfinal - pinitial = pfinal, since pinitial = 0.
After 1.4 s the force is zero, there is no acceleration, the cart is moving with constant speed.  Use the step up button to step to t ~1.4s.  Then calibrate and start taking data.   Find the position of the cart as a function of time.   Import your data into Excel.

Start with the impulse_1.mp4 clip.  To play a video clip or to step through it frame-by-frame click the "Begin" button.  The "Video Analysis" web page will open.


Repeat for the impulse_2.mp4 clip.

To earn extra credit add your name and e-mail address to your spreadsheet.  In full sentences answer the following question.

Save your Excel spreadsheet (your name_ex7.xlsx), go to Canvas, Assignments, Extra Credit 7, and submit your spreadsheet.