Partners: Matthew Ibarra, Billy Justin
Date of Lab: 12 October 2016
Lab 14 Ballistic Pendulum
Mission Statement:To determine the firing speed of a ball from a spring-loaded gun.
Theory: In this lab, we were examining an inelastic collision in which momentum is supposedly conserved when a small steel ball, moving at some unknown velocity, is propelled into and absorbed by a nylon block , in turn imparting its kinetic energy into the nylon block, which in turn rises through some angle that we measured.
Experimental Procedure:
Below is the setup of our experiment.
As shown in the picture above, the mechanism involves a notched spring-notch bolted with three different notch settings. The nylon block is suspended by four vertical strings, themselves attached to a protruding plate with tighteners on it to modify the tension on each string. Also attached to the protruding plate was the angle indicator. After properly setting up the system, we pulled the punch to the third notch, inserted the steel ball, stabilized the nylon block, aligned the angle indicator, got behind the punch, and fired away.
We failed multiple times to have the ball lodge itself within its designated slot in the nylon block, but after about seven attempts we finally succeeded in conducing a supposedly inelastic collision between the two. After getting another four successful inelastic collisions, we proceeded to get an average. We carried out our calculation using the information we collected from our trials (namely the angle and mass of the ball and block), shown below.
We obtained a velocity of 6.04 m/s.
Next, we calculated the propagated uncertainty of our experiment, shown below.
As shown above, the calculated uncertainty in our answer was +/- 0.15 m/s
Lastly, we were supposed to find out the actual distance the ball would travel by conducting a projectile motion trail and accompanying calculation, shown below.
Conclusion:
Following our projectile motion problem, we observed that the firing velocity of the steel ball had to be within 0.15 m/s of our value calculated using conservation of momentum equations. Sure enough, we were approximately 0.1 m/s off, which is within our propagated uncertainty tolerance. Sources of error would doubtlessly include the asymmetric application of tension by each string regardless of how evenly we tried to tighten and align them, followed by the possibility that an external force did indeed act on the system while the steel ball impacted the nylon block, thus rendering this collision not truly inelastic.
Experimental Procedure:
Below is the setup of our experiment.
As shown in the picture above, the mechanism involves a notched spring-notch bolted with three different notch settings. The nylon block is suspended by four vertical strings, themselves attached to a protruding plate with tighteners on it to modify the tension on each string. Also attached to the protruding plate was the angle indicator. After properly setting up the system, we pulled the punch to the third notch, inserted the steel ball, stabilized the nylon block, aligned the angle indicator, got behind the punch, and fired away.
Next, we calculated the propagated uncertainty of our experiment, shown below.
Lastly, we were supposed to find out the actual distance the ball would travel by conducting a projectile motion trail and accompanying calculation, shown below.
Conclusion:
Following our projectile motion problem, we observed that the firing velocity of the steel ball had to be within 0.15 m/s of our value calculated using conservation of momentum equations. Sure enough, we were approximately 0.1 m/s off, which is within our propagated uncertainty tolerance. Sources of error would doubtlessly include the asymmetric application of tension by each string regardless of how evenly we tried to tighten and align them, followed by the possibility that an external force did indeed act on the system while the steel ball impacted the nylon block, thus rendering this collision not truly inelastic.
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