Question

A Ball is thrown vertically upward . It goes to the height of 19.6 m and then returns back to the ground . Find the initial velocity of the ball, total time of the journey, final velocity of the ball when it strikes the ground.

Answer 1

Let the initial velocity be u

Max. height reached, h = 19.6 m

Velocity at maximum height = 0

Using,

v² = u² – 2gh

=> u² = (2)(9.8)(19.6)

=> u = 19.6 m/s

The net displacement of the ball is zero. So,

S = ut – ½ gt²

=> 0 = 19.6t – (0.5)(9.8)(t²)

=> t = 4 s

Velocity of the ball after 4 s is thus the final velocity,

v = u – gt

=> v = 19.6 – (9.8)(4)

=> v = -19.6 m/s

The negative sign implies that the final velocity is in downward direction.