### C. “Partially” Elastic Collisions

This part of the experiment precedes much like the first part except that now we will only be using one cart. We will push the cart and it will strike a wall, and recoil backwards.

9. Use one cart and place the Force sensor on it. Be sure to screw it down using the Phillips head screwdriver located on the front table.  We will be using Motion Sensor (which is already setup) with our Force Sensor. The Force Sensor now needs to be setup. Double-click it after you have dragged it over to the Experimental Setup window onto the first analog channel. In the general tab click Fast Force Changes (collision). Then change the sampling rate to 500 Hz by clicking the + button. It is now set to run. You may still have old data showing in the other two graphs. Click each graph and then the Data button and then select No Data. If linear momentum is conserved, the following relationship is valid:

.

In this equation m1 is the mass of the cart, m2 is the mass of the "target", v1 is the velocity of the cart, v1' is the velocity of the incident cart after the collision and v2' is the velocity of the "target" after the collision.

10. Run the Experiment. We now want to calculate the change in momentum of the cart due to the collision, from the velocity measurements and the force measurements. Calculate the change in momentum from the velocity measurements as you did before in the inelastic case. Now calculate the change in momentum from the Force Sensor measurements. We know that the Impulse is the area under a Force vs. Time graph. This is exactly what we have with the Force Sensor. Click drag in the F vs. t graph to select the collision. Use the expand graph button . Now under the statistics menu choose Area. On the graph you should see the Impulse calculation. Make sure to get a print out of the Velocity, Acceleration, and Force graphs for your notebook.

11. Does the change in momentum (Impulse) determined from the Velocity measurement agree with the change in momentum from the Force measurement?

12. Is momentum conserved? Why or why not?

13. Do you think that KE is conserved? Why or why not?

Note: you need to turn in a Velocity and Acceleration graph from experiment 1 and a Velocity, Acceleration, and Force graph from experiment 2.