Engineering
Physics
Collision
Question

A particle of mass m moving with a speed v hits elastically another particle of mass 2m at rest, on a horizontal smooth circular tube of radius R.

The time after which the next collision will take place is equal to πR/v 

Speed of 2m just after collision will be 2v/3

Speed of m just after collision will be v/3

Velocity of separation just after first collision will be v

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Solution

Let the final velocity of 2m and m be V2 and V1 respctively.
2mV2 + mV1 = mV        ......(1)

e=1=V2-V1 V  ........(2)

 On solving,   V1=-V3, V2=2 V3

Vsep = V2 – V1 = V

t=2πRVrel=2πRV.