group+014

media type="file" key="project.mov"

Our group's experiment will analyze the conservation of momentum from one pool ball to another as they collide. We set up a ramp on the pool table and let a purple ball roll down to hit a green ball. We then measured the distance and angles that the two balls rolled. We found velocity of the single ball rolling down the ramp by measuring how long the first ball took to roll down the ramp, how long they took to stop and how far it rolled. After we find the velocity of the green ball after it came into contact with the purple ball, we will be able to prove that the momentum was conserved in the elastic collision.

Equipment:
 * Pool table, pool balls
 * Two rulers
 * Protractor
 * Ruler, masking tape, stopwatch
 * video camera
 * meter stick

Safety Precautions:
 * Don't stop the pool balls with your hands while the ball is still rolling.
 * Don't wear flip-flops in case the pool ball drops
 * Ensure that others are aware that the experiment is in motion

Procedure: 1. Find the mass of each pool ball 2. Measure the angle between the ramp and the pool table 3. Place one pool ball on the ramp and let it roll down the ramp until it comes to a complete stop 4. Measure the length of the ramp 5. Measure the distance from the bottom of the ramp to the point where the ball stopped 6. Use trig to find the height from the table to the top of the ramp 7. Find the velocity of the ball as it leaves the ramp by setting its potential energy equal to its kinetic energy because all of the potential energy was transferred to kinetic energy when the ball reached the bottom of the incline 8. Multiply the mass of the ball by the velocity to find the ball’s momentum 9. Find the friction of the table by assuming a constant velocity for the ball. Find the force of friction by multiplying the force of gravity times the mu 10. Since the force of friction is the work done to stop the ball, set the equation for work equal to the equation for kinetic energy because as the ball slowed down to a stop, it lost kinetic energy. The equation for work is force times distance, so substitute in the equation for the force of friction, and the distance it took for the ball to come to a complete stop. Use the velocity of the ball as it left the ramp to substitute into the kinetic energy equation. 11. Solve for the mu 12. Perform the experiment—set up a second pool ball at the end of the ramp and let the original ball roll down the ramp so that they collide 13. Measure the distance both balls rolled and their angles 14. To find the velocity of each ball after the collision, again set the work equation equal to the kinetic energy 15. Since the balls rolled in different directions after the collision, you must add the vectors by using trig to find the velocity of the balls in the horizontal direction 16. Multiply the velocities by the masses of each ball and add the resulting momentums together 17. Compare the final momentum after the collision to the initial momentum of the single ball







Conclusion: In the end, the collision of the two pool balls demonstrated the conservation of momentum. In theory, the initial momentum should equal the final momentum, which would correctly represent the idea. In our case, momentum was conserved because the initial momentum, before the collision(.025), is relatively similar to the final momentum, after the collision(.018).

Sources of error: The percent error between the actual and the theoretical is about 28%. Some types of error include:
 * 1) The actual measurement from the bottom of the ramp to where the pool ball landed. This was difficult to measure because the pool balls are round and so to measure the exact center of where the balls ended up, we had to make a close prediction
 * 2) The measurement of the angles from the ramp and the angles between the two balls. The protractor made it a whole lot easier, however, sometimes it can have some close calls.
 * 3) Rounding helps to simplify big numbers so we can calculate easier and faster. Rounding also gives problems because the more rounding, the more chance of a bigger percent error. The answer might not be as specific.