A balloon is moving along with constant upward acceleration of `1 m//s^2`. A stone is thrown from the balloon downwards with speed `10 m//s` with respect to the balloon. At the time of projectile balloon is at height `120 m` from the ground and is moving with speed `20 m//s`. Find the time required to fall on the ground by the stone after the projection.

Options

A. 6 sec
B. 4 sec
C. 3 sec
D. 4.5 sec

Answer

A

Explanation

`-120 = 10 t (1)/(2) - xx 10 xx t^2`
`t^2 - 2t - 24 = 0`
`t = 6 sec`.