A ball is thrown upwards from the top of an incline with angle of projection `theta` with the vertical as shown. Take `theta = 60^(@)` and `g=10 m//s^(2)` . The ball lands exactly at the foot of the incline.

The time of flight of the ball is:

Options

A. (a)`t=sqrt(3) s`
B. (b)t = 4 s
C. (c)t = 3 s
D. (d)t = 6 s

Answer

C

Explanation

`u_(y)=10 cos 60^(@) =5m//s rArr 5t-1/2 gt^(2)=-30 rArr t^(2)-t-6=0 rArr t=3s `