Impulse and change of momentum

1. Collision of a cart with the force probe

Calibrate the force probe. Be sure to check its calibration several times during this part of the laboratory. Mount the force probe on the stand at one end of the track. Position the motion detector at the other end, facing the force probe. Roll a Pasco cart (flat side facing the force probe) toward the force probe so that it "gently" collides with the probe. Measure the position of the rolling cart and the force exerted on it by the probe during the collision. Select a collection rate, an "averaging" and a time scale which will give you detailed knowledge of the collision. Make a number of practice runs until you are satisfied that you have made the best selections. Record your settings.

Determine the change in momentum ( p in the x direction of motion) of the cart during the collision:

(Eq. 1)

and the impulse I, delivered by the force probe to the cart during the collision can be found using Integral in the Analyze Menu:

(Eq. 2)

If no other forces are acting on the cart in the direction of motion during the collision , then we should expect agreement:

(Eq.3)

Do they agree?

Repeat the collision for two other initial cart speeds (make sure that the cart's wheels stay on the track before and after hitting the probe) .

Do your results regarding Eq. 3 depend on the initial speed?

2. Collisions between carts

For this part of the lab you will use only the video camera to document with iMovie the different cases, and use LoggerPro to analyze the data as in Lab 2.

2a) Roll one cart from each end of the track toward the center so that the carts collide (spring sides facing each other). Determine the change in momentum of each cart. Compare the change in momentum of cart one to the change in momentum of cart 2. According to theory:

(Eq. 4)

Find also the fractional change, f, in kinetic energy of the two-cart system:

Repeat this procedure with an added mass in one cart and then for a second added mass in the same cart.

Do your results agree with Eq. 4?

2b) Set the spring mechanism fully in on both carts. Place the carts so that they are at rest on the track, but touching with the springs facing each other and kept together by the velcro contact. Using a rod release the spring mechanisms (releasing one should release the other). Compare the change in momentum of cart one to the change in momentum of cart 2. Find Kf.

Repeat this procedure with an added mass in one cart and then for a second added mass in the same cart.

Do your results agree with Eq. 4?

Compare Kf for the three trials.

2c) Push in the spring mechanisms so that the velcro in the carts may get in contact. Gently roll one cart from one end of the track toward a stationary cart placed at the center. The carts should move together after the collision. Analyze momentum and kinetic energy for the system of two carts.

Repeat this procedure with an added mass in the stationary cart and then for a second added mass in the same cart.

Do your results agree with Eq. 4?