Question

a cricket ball is dropped from a height of 20 m.
a) calculate the speed of the ball when it hits the ground.
b) Calculate the time it takes to fall through this height ( g =10m/s^2 )
[ my doubt is - in the question. b. can we use v= displacement / time formula to find time]​

Answer 1

To solve this problem we need to use rhe formula,

v^2 - u^2 = 2gh

Where, v is final velocity, u is initial velocity, g is acceleration due to gravity and h is the height from which distance is thrown.

Here,

v = ?

u = 0 m/s

g = 9.8 m/s

h = 20 m

Therefore,

v^2 - u^2 = 2gh

?^2 - 0^2 = 2 × 9.8 m/s × 20m

? ^2 = 392

? =√392

? = 19.7989899.

Therefore, the ball will touch the ground with a speed of 19.7989899 (approx).