Part B: Ballistic Pendulum
The questions n the very bottom ispertaining to a lab over projectile motion and its asking to useequations on the bottom to find velocity. Below are the proceduresof the lab and the necessary data to find initial velocity.
- Place the ball in the launcher and cock the gun until thespring is locked in the same position as used for the previouspart. Fire the gun. The ball will enter the catcher in thependulum, which will swing up and return. A slider indicates themaximum angle by which it had moved. Repeat this procedure fivetimes and obtain the average. Use the average angle and the lengthof the pendulum L (distance from pivot to its center of mass) toobtain the vertical distance ‘h’ moved by the center ofmass of the pendulum+ball. (You will need to do some trigonometryto get ‘h’)
- In some instruments, as the pendulum swings up, it comes torest on a curved rack. For this instrument, record the verticaldistance between the base of the apparatus and the center of massof the pendulum+ball before it swings and after it stops. Thedifference is the vertical height ‘h’.
- Use equations 1, 3 and 4 to obtain the initial speed of theball. Compare this with the value obtained from part 1.
Calculate the average value for thevertical distance h the pendulum-ball system has risen after thecollision. This is the difference between the height of CM at itshighest point and that at its lowest point.
1Â Â
Gain in Potential Energy = Loss inKinetic Energy
Potential Energy at highest point=
Mass M of pendulum: 240 grams Mass mof ball: 64 g
| Trials | 1 | 2 | 3 | 4 | Avg |
| Angle of CM at its lowest point | 0o | 0o | 0o | 0o | |
| Angle of CM at its highest point | 33o | 35o | 40o | 40o | |
| Angle (highest - lowest) | 33o | 35o | 40o | 40o | |
| Distance L from pivot to CM of pendulum | .285 meters | .284 meters | | | |
Kinetic Energy at lowest point =Â Â Â Â Â Â Â
Height h from angle and L= ?
Velocity V1 of pendulum as it startsto swing=?
Velocity Vo of ball=?
Calculate the average value for thevertical distance h the pendulum-ball system has risen after thecollision. This is the difference between the height of CM at itshighest point and that at its lowest point.
Using Energy balance and momentumconservation equations, calculate the initial velocityV0 of the projectile.
