Lab 15: Collisions in Two Dimensions

Lab 15: Collisions in Two Dimensions

Lab Members:

Jarrod Griffin

Christina Vides

Enio Rodriquez

The purpose of this lab is to check if kinetic energy and momentum are conserved in a two dimensional collision.

Introduction:

In this lab we used a glass table, two small balls, a computer and our smartphone cameras in order to complete this experiment. We used our smartphone cameras on a slow motion setting in order to get a video file we can analyze in Logger Pro and get precise position measurements for each ball. From these position measurements, we can find the velocity of the balls before and after the collision.

Apparatus/Procedure: 

We set up our lab as described in the lab manual, except instead of using a camera that connects to our laptops, we used the cameras on our smart phones that can record at a higher frame rate, giving us more frames per second to collect data from. We wanted this so that we could get more precise data, giving us more real world results. Once we collected our data and analyzed it in Logger Pro, we used linear fits before and after the collision in order to give us velocities for both balls before and after collision. A sample of the apparatus is pictured below. 

In order to check to see if kinetic energy and momentum were conserved, we found the velocity as mentioned above, and plugged them into our two equations for conservation of energy and momentum.  We repeated this experiment two times with two different types of balls, metal, and clear/glass.

After Collision between Glass and Steel:


Before Collision between Glass and Steel:

Data/Calculations:

Steel Ball vs Glass Ball:

This is a sample calculation done. I did this type of calculation for the other set of balls that collided. For the above calculations, I used the conservation of energy equation in order to verify if the energy was conserved, which it was not. I also used the conservation of momentum equation to check if it was, which it was.

We calculated the velocity of the center of mass by using a linear fit in Logger Pro. We found the position on the center of mass by using a feature built into Logger Pro that plotted the position of center of mass if given the masses of the two objects.

Graphs:

Conclusion:

In this lab, we showed that momentum was in fact conserved, while kinetic energy was not. We lost kinetic energy due to small amounts of heat, friction, and sound. We proved this by finding the velocities of both balls before and after impacts, and by then using the conservation of momentum and kinetic energy theorems to verify if the energy and momentum were actually conserved. We had predicted that momentum would be conserved, but that energy would not be, which we proved to be true.