The solid rubber balls A and B having masses 200 and 400 gm respectively are moving in opposite directions with velocity of A equal to 0.3 m / s . After collision the two balls come to rest, then the velocity of B is

Options

A. 0.15 m/sec
B. 1.5 m/sec
C. `– 0.15 m/sec`
D. None of the above

Answer

C

Explanation

Initial linear momentum of system `= m_(A) vec(v)_(A)+ m_(B) vec(v)_(B)`
`=0.2 xx 0.3 + 0.4 xx v`
Finally both balls come to rest
`therefore` finall linear momentum = 0
By the law of conservation of linear momenum
`0.2 xx 0.3 +0.4 xx v= 0`
`therefore v_(B)= -(0.2 xx 0.3)/(0.4)= -0.15m//s`