A solid disc of mass M is just held in air horizontally by throwing 40 stones per sec vertically upwards to strike the disc each with a velocity 6 `ms^(-1)`. If the mass of each stone is `0.05kg` what is the mass of the disc `(g=10ms^(-2))`

Options

A. 1.2 kg
B. 0.5 kg
C. 20kg
D. 3kg

Answer

A

Explanation

Weight of the disc = force applied by bullet
`rArr Mg = nmv rArr m = (40 xx 0.05 xx 6)/(10)`
` = 1.25 kg `