Lab 14 - Ballistic Pendulum

Purpose: The purpose of this lab was to determine the initial velocity of a fired projectile.
Apparatus: Our setup for this lab was a something called a ballistic pendulum. A fixed, stationary gun is aimed at a hanging block of measured mass 0.0805 (+/-)0.001kg. The mass of the projectile is also measured using a scale which results in a mass of 0.0075 (+/-)0.001kg. After the projectile is fired, it becomes lodged in the hanging block and the system swings upwards because of the fact that the block is held up by four strings of negligible mass.
Procedure: The procedure was straight-forward. We placed the projectile in the gun, moved out of the direction of its path, and fired it into the block. The block and ball(projectile) moved together after they stuck and rose to an angle of 16.7 degrees. After we plugged in the values for the masses, and the angle, and the length of the string, which was 0.0206 (+/-) 0.005m, we then were able to calculate the initial firing speed of the gun. We ran multiple trials and figured out that the firing velocity of the ball before impact was 4.73m/s. Afterwards, we cleared a path and moved the hanging block out of the way. We then placed the gun facing the edge of the table. We then placed a sheet of carbon paper on top of a blank sheet of paper on the ground in order to find out where the ball hits the ground after the gun is fired away from the edge of the table. Then, using some simple kinematics and a meter stick, we calculated that the actual firing velocity of the gun was 5.612m/s.
Theory: The theory behind this experiment is that when an object becomes lodged in another, momentum is conserved. So we used the law of conservation to guide us in the right direction. We then set KE=GPE, where KE is before impact and GPE is after impact. However, for momentum to be conserved we had to use the mass of the ball only in the KE formula, and the combined masses of the ball and the block for the GPE formula. In the GPE formula, we multiplied "g" by (L-LcosΘ) in order to get the vertical component of the direction of travel of the block.

Conclusion: What we noticed was that the velocity we calculated from the block moving up after the ball embedded in it was significantly lower than when we just fired it off the edge of the table. This shows that although momentum is conserved in a collision, energy is not. A lot of the energy that was lost was due to heat. The professor showed us a proof on the board by using the formula q=mct. So it is very possible that all of the energy that was lost was converted into heat. This lab was a good representation for how in collisions, momentum is conserved but energy is not. We saw it firsthand, and there is no denying it.
 My partners  for this lab were Elliot Sandoval, Sherri(?) and the person she sits next to. (I forgot to get their names).