Collisions Lab

Big Question:

"What is a better conserved quantity - momentum, or energy?"
-After completing our collisions lab and collecting our data, we found that momentum is a better conserved quantity as opposed to energy. With energy, both cars start out with kinetic energy, but when they collide, the energy is transfered to heat, or possibly friction. 

Lab Work:
      We began our lab by setting up two cars on a track facing each other. On either end of the track itself we had sonar sensors which would allow us to calculate the velocity of the cars. Our first test was "elastic" meaning that each car would have springs colliding with each other on the ends of the cars. The red car was stationary and we rolled the blue car into it. The blue car stopped moving and the red car was pushed down the track.This was our first test for the "elastic" collision.

      Our second test was an "inelastic" collision where we took the springs away from the cars. This time, when we ran the blue car into the red car, both cars stayed together and continued rolling down the track. 

      Our data involving momentum, energy, and velocity are recorded below:

(We used the formula, P = mv, to calculate momentum, and the formula, K = 0.5mV^2, to calculate the energy.)

Percent Difference:

      This whiteboard shows how we calculated the percent difference of energy and momentum. We calculated the percent difference of the energy and momentum by first subtracting the "before" number from the "after" number. Then we divided that number by the average of the two numbers. We then took that number and multiplied it by 100 to give us our percent difference value.

Real World:

      In our world today, one of the most obvious examples is a car crash. When one car crashes into the other, both of the cars continue moving a little. The kinetic energy of the cars is transfered into heat or friction and the momentum of the cars is conserved. This is an example of an "inelastic" collision as performed in our lab.