17-Nov.-14: Conservation of Angular Momentum

PURPOSE:

To verify that Angular Momentum is conserved for a swinging meter-stick/clay collision apparatus.

This required suspending a meter-stick at one end with the other end freely swinging. The goal is to have the free-swinging-end of the meter-stick collide with a stationary piece of clay (so it sticks). Our expectation is that the from a known initial height the meter-stick has some Potential Energy - as it swings it gains Kinetic Energy, and it then rises again after the collision to a new height gaining a different amount of Potential Energy because of the now attached piece of clay. Our goal is to measure the new rising height after the collision and analyze our measurements to determine if angular momentum is conserved.



APPARATUS:








Equipment:

A meter-stick, secured at one end to freely swing, with minimal friction. - mass = 80-g
A piece of clay for the meter-stick to collide with. - mass = 28-g
A camera to capture the height the clay rose to after the collision.



EXPERIMENT:

1. We began by weighing the mass of the meter stick and the piece of clay.
   
2. We set up the camera - adjusting any necessary settings, such as, the exposure, focus, or gain.
   
3. We then analyzed the collision through calculation, using conservation of energy to find the angular velocity of the stick just before the collision.
   
4. After finding the angular velocity just before the collision, we used conservation of angular momentum to find the angular velocity after the collision.
   
5. With the angular velocity after the collision, we use conservation of energy again to find how high the piece of clay should go. The expected final height was calculated to be h = 0.108-m.
   
6. We began performing the experiment by raising the meter-stick to a 90 degree angle, parallel with the ground. This means that its change in potential energy from the initial 90 degrees to the point just before the collision is mg(L/2) because the center of mass of the meter-stick is located at its midpoint.
   
7. As we released the meter-stick we began a video capture. We recorded the swing until we saw the swing change direction, which is where the maximum height after the collision is.
   
8. From the video capture, we tracked the position of the piece of clay, frame by frame, by plotting the position of clay. With a meter stick in the background of our video capture we were able to scale our plotted points, and find the actual maximum height. h_actual = 0.08-m
   
   

CONCLUSION:

The height we predicted was 0.108-m and the height we measured was 0.08-m. Our predicted value for the height was higher than the actual value due to the fact that any frictional components in our apparatus were intentionally neglected.

A Great Day for Physics

(11/17/14, 7:08am)