A ball is thrown vertically upwards. It goes to a height 19.6 m and then comes back to the ground, Find the initial velocity of the ball .
Take g = 9.8 `m s^(-2)`

Explanation

Given , h = 19.6 m , a = - g = - 9.8 m` s^(-2)` , v = 0
Let t s be the time taken by the ball to reach the highest point.
From equation of motion v= u + gt
0 = 19.6 - 9.8 t or 9.8 t = 19.6
`therefore t = (19.6)/(9.8) = 2s`
It will take the same time t = 2 s to come back from the highest point to the ground .
`therefore` Total time of journey `t. = 2t = 2xx 2 = 4s`