A man in a balloon rising vertically with an acceleration of `5 ms^-2` releases a ball `2` second after the balloon is let go from the ground. The greatest height above the ground reached by the ball in meter is : `(g = 10 ms^-2)`.

Options

A. 20
B. 15
C. 30
D. 5

Answer

B

Explanation

Height ascended by balloon in `2 s` :
`s_1 = (1)/(2) xx 5 xx (2)^2 = 10 m`
Velocity of balloon after `2 s` :
`v_1 = 5 xx 2 = 10 m//s`
This will also be the velocity of ball when released from balloon. So further maximum height ascended by ball.
`s_2 = ((10)^2)/(2 xx 10) = 5 m`
Total height : `s = s_1 + s_2 = 10 + 5 = 15 m`.