Question

$....$
. A ball is thrown vertically upwards. It goes to a height 20 m and then returns to the
ground. Taking acceleration due to gravity g to be 10 ms , find :
(a) the initial velocity of the ball
(b) the final velocity of the ball on reaching the ground and​

Answer 1

Answer:

Given:

s (distance) = 20m

a (acceleration) = 10m/s²

v (initial) = 0

u (final) =?

a) initial velocity of the ball :

v²-u²= 2as ( using 3rd equation of motion)

0²-u² = 2×10×20

=> u = √20×20

=> u = 20

Thus, initial v. of the ball = 20m/s

b) final velocity of the ball after reaching the ground :

v²-u² = 2as (using 3rd equation of motion.)

v²-0² = 2×10×20

=> v = -√2×10×20

=> v = -√20×20

=> v = -20.

Thus,final v. of the ball = 20m/s ( in negetive direction)

follow me ♥