Purpose:
To verify the principles of conservation of momentum and angular momentum
Equipment:
Air Table with Air Pump and Pucks
Document Camera
Scale and ruler
Flash drive.
Experiment:
1. Set up the table as shown in the photo.
2. Place one puck in the middle of the air table. Practice collisions with spinning pucks!
You will create and film three separate collisions. For each collision, the instructor or lab assistant will video-tape at least one collision for each lab group and store on a flash drive or hard drive so that your lab group will have access to it.
3.
For the first collision, your goal is to have a spinning disk strike the stationary disk at a glancing angle. After the collision, the stationary disk should move off at an angle relative to the incoming disk. The spin rate should change after the collision.
4. For the second collision, you will use two “Velcro pucks.” A spinning puck should strike the stationary puck at a glancing angle so that the two pucks stick together and continue spinning together.
5. For the third collision, you will attach one puck to a post at the center of the table by a string. You should try to strike the “tethered” puck more or less directly so it revolves around the post after the Collison.
6.
If time permits, feel free to create your own collision and film for analysis.
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LPC Physics
Conservation of Momentum I
7. Record the masses and radii of the pucks involved in your collisions.
Analysis and Results
1. Open the first move in QuickTime and play it through. Now, step it through and observe how the “clock” changes as you step through. In order to analyze linier momentum, and angular momentum you will need to determine the time interval between frames. To do this, observe the time measurement in QuickTime while you count the number of frames to determine the “frames/sec”. Then invert to calculate seconds per frame.
2. Return to the beginning of the movie. Use the rulers in your “scene” to measure the horizontal and vertical displacements as you step through images on the movie. This will allow you to measure the average x and y velocities of the pucks before and after the collision. You can also count the rotate rate of each puck to determine the angular momentum. 3.
Calculate the x and y momentum of each puck before and after the collision.
Determine if momentum is conserved in both the x and y directions.
4. To see if Angular momentum is conserved, measure the spin rate of each puck before and after the Collison. Determine if the angular momentum (Iω) of the incident puck equals the total angular momentum of both pucks after the collision.
5. Repeat steps 9 – 11 for the second collision where
