A particle of mass `m` moving with horizontal speed `6 m//s` as shown in the figure. If `m lt lt M` then for one - dimensional elastic collision , the speed of lighter particle after collision will be

Options

A. 2m/sec in original direction
B. 2 m/sec opposite to the original direction
C. 4 m/sec opposite to the original direction
D. 4 m/sec in original direction

Answer

A

Explanation

`v_(1)= ((m_(1)-m_(2))/(m_(1) + m_(2))) u_(1) + (2m_(2) u_(2))/(m_(1) + m_(2))`
Substituting `m= 0, v_(1)= -u_(1) + 2u_(2)`
`rArr v_(1)= -6 + 2(4) = 2m//s`
i.e. the lighter particle will move in original direction with the speed of 2 m/s.