Study conservation of momentum in elastic collision.

This experiment shows conservation of momentum in elastic collisions using trolleys on a track, verifying momentum before and after the collision.

APPARATUS:

Friction-compensated track, two trolleys, ticker timer with double tape, meter rode, stopwatch, stroboscopic disc.

PROCEDURE:

1.  Adjust the track as in experiment No.7.
2.  Fix a metallic nose (instead of a cork as in the previous experiment), take a bracket, and the length of ticker tape to the trolley No. 1. Fix another table bracket and tape to the trolley No. 2, as shown in the diagram.
3. Pass both tapes through the same ticker timer. Use two carbon discs back to back and pass one tape above the upper disc and the other below the lower disc.
4. Place trolley No. 2 in the middle of the track as shown in the diagram.
5. Start the ticker timer and push trolley No. 1 gently to collide elastically with trolley No. 2.
6. Analyze the tapes and find the velocity of each trolley before and after the collision.
7. Calculate the momentum and see that the momentum of the system before the collision is equal to the momentum of the system after the collision. If there is some difference, ignore it.
8. Repeat the experiment three times with different loads on the trolleys.
9.  The experiment can be performed on a horizontal track if the friction is negligibly small.

OBSERVATION AND CALCULATION:

Frequency of the ticker timer              = f = …dots/sec.

BEFORE COLLISION:

No. of obs.	Mass of the trolley No.1. m1 (gm). 1	Velocity of the trolley No.1 v (cm/sec.)	Momentum of the system before collision m1v (gm-cm/sec.)	Mass of the trolley no.2. m2(gm)
1. 2. 3.

No.of obs.	Mass of the trolley No.1. m1 (gm). 1	Velocity of the trolley No.1 V (cm/sec.)	Momentum of the system before collision m1v (gm-cm/sec.)
1. 2. 3

AFTER COLLISION:

No of obs.	Mass of the trolley No.1. m1 (gm). 1	Momentum of the trolley No.2. m1 v2 (gm-cm/sec.)	Total momentum of the system after collision (m1 v1 + m2 v2) (gm-cm/sec.)
1. 2. 3.

PRECAUTIONS

The precautions are the same as those in Experiment No.7.

• Use fresh carbon discs in the time ticker.
• To avoid an inelastic collision, the first trolley should not be pushed violently.
• Use very small lengths of the tapes for measuring the velocities of the trolleys.

                                                                                      VIVA COCE

Q.1.       What is an elastic collision?

Ans.      A collision is an elastic collision if the momentum and the kinetic energy of the system remain constant before and after the collision.

Q.2.      Why is trolley No.1.is pushed gently in this experiment?

Ans.    If we push the first trolley violently, it may move the second trolley as one after a collision, and the collision may be inelastic.