Question

A ball is thrown vertically upwards with a velocity of 49 ms–1. Calculate
(a) the maximum height to which it rises.
(b) the total time it takes to return to the surface of the Earth.

Answer 1

i)Maximum Height=122.5 m

ii)Total time taken = 5 s.

Explanation:

We have to find the maximum height,

$Maximum\ height =v^2 = u^2 -2gh$ ,where v is final velocity

=0,

Here, if the ball reaches its maximum height h, u is initial projection velocity.

 Hence we have, 0 = $49^2 -2\times9.8\timesh$  

                            h = 122.5 m

Maximum Height to which a ball rises=122.5 m

We also know that, Maximum height is v = u - gt ,

Since here v = 0 ,  

t = u/g  

   = 49/9.8

 t  = 5 s

The total time it takes to return to the surface of the Earth = 5 s.