An isolated particle of mass `m` is moving in horizontal plane` xy` along the `x`-axis, at a certain height above the ground. It suddenly explodes into two fragment of masses `m//4` and `3m//4`. An instant later, the smaller fragment is at `y=+15` cm. The larger fragment at this instant is at

Options

A. `y=-5cm`
B. `y=+20cm`
C. `y=+5cm`
D. `y=-20cm`

Answer

A

Explanation

Before explosion, particle was moving along `x`-axis, i.e., it has no `y`-componet of velocity. Therfore the centre of mass will not move in `y`-directioni or we can say `y_(CM)=0`
now, `y_(CM)=(m_(1)y_(1)+m_(1)y_(1))/(m_(1)+m_(2))`
Therefore, `0=((m/4)(+15)+(3m//4)(y))/((m/4+3m//4))`
or `y=-5cm`