Momentous Tennis Balls

Modeling Conservation of Momentum With Tennis Balls

For this blog assignment, I decided to model the conservation of momentum using the collision of two tennis balls.  First, I weighed the tennis balls on a scale, to get the mass value of each. 

Next I took a video (after many attempts) with one of the tennis balls at rest, and me pushing the other tennis ball toward it, giving it a velocity. The first tennis ball continued moving at a reduced speed after the collision, while the other tennis ball started from rest after the collision and moved in the same direction as the first one. A ruler was used to provide Logger Pro with a scale. Check out the video below!

Using Logger Pro, I then analyzed the velocities of both the tennis balls before and after the collision. Below is the graph of Time vs. Velocity B1 and Velocity B2.   

Using the equation below, I chose two times, one right before the collision and one right after. 

  M1 * V1  + M2* V2 = M1*V1F + M2*V2F

  0.056 kg * 1.296 m/s   + 0   =  0.056 kg * 0.205 m/s + 0.056  kg * 0.620 m/s  

  0.07205   =    0.0538

As you can see above, momentum was not perfectly conserved in my collision, mostly likely due to error with the video or the plotting of the points (I am far from a Pro). In addition, there is friction between the tennis balls and the counter that was not accounted for. However, the two momentum's are close to each other, and the shape of the graph also demonstrates the conservation of momentum. 

Kinetic Energy Lost: 

KE Initial =  0.5 * 0.056 kg * 1.296^2 = 0.046595

KE Final =  0.5 * 0.056 kg * 0.205^2  +  0.5 * 0.056 kg * 0.620^2  = 0.01194

KE Lost =  0.03465 J

This kinetic energy could be lost to heat.  In addition it could be lost to friction between the balls and the counter. 

**Disclaimer: Neither I nor anyone in my family play tennis, these were taken from the laundry room.