Collisions Lab

Collisions Lab

Purpose: The purpose of this lab was to better understand the difference between elastic and inelastic collisions, and what affect each had on the vector and scalar quantities, specifically momentum (vector) and kinetic energy (scalar).

Background:                                         Scalar vs. Vector:

Elastic vs. Inelastic

Procedure: We put two carts (red and blue) of equal mass (.25kg) on each side of the track. We also put two range finders on each end of the track to measure each carts velocity. To record our data we plugged the range finders into the force probe and the force probe into the computer. By doing this we were able to easily measure the velocity (on the graph) of both carts before, during, and after the collision took place. First we did an elastic collision and pushed our red cart(with the spring out) to the right towards the blue cart(also with the spring out). After this collision took place both cars continued to move to the right, but the red cart followed the blue cart at a much slower speed. The next collision we did was an inelastic collision, and again we pushed the red cart to the right toward the blue cart. After this collision though the two carts stuck together (because of the velcro) and both continued to move to the right together.

Data: We then measured the velocity, momentum, and kinetic energy both before and after the collisions. Then we added the two(before and after) together to find the totals of all three of these things.

 Then we found the percent difference of both momentum and energy.

Elastic Collision:

                                

Inelastic Collision:

From this we were able to find the momentum is better conserved than energy(smaller percent difference=less energy given off during a collision). Also that more energy is lost in inelastic collisions than in elastic collisions.

Equation Time!

Momentum: 

P=mv

• P=momentum
• m=mass
• v=velocity

Percent Difference:

(Total Before-Total After)/ (Total Before+ Total After/2)(100)

Real Life Connection:

The concept of momentum in collisions relates to the game of pool. You exert a certain amount of force (using the pool stick) on the white ball. The white ball then (if you actually have an accurate shot) hits one of the colored balls. When it collides with colored ball the colored ball bounces off of the white ball and hopefully into the pocket. This is more of an elastic collision because the white ball does not stick to the colored ball, but still moves in that general direction most of the time.