To study the conservation of momentum in case of an elastic collision.

APPARATUS:

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

PROCEDURE:

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

• Use fresh carbon discs in the time ticker.
• To avoid 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 collision.

Q.2.      Why 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 collision and the   collision may be inelastic.