Question

What is the velocity on impact of a ball dropped from a 20 m cliff?

Answer 1

`19.799m/s`

Explanation:

Data:-
Initial Velocity`=v_i=0` (Because the ball is dropped not thrown)
Final Velocity`=v_f=??`
Height`=h=20 m`
Acceleration due to gravity`=g=9.8m/s^2`
Sol:-

Velocity on impact is the velocity of the ball when it hits the surface.

We know that:-

`2gh=v_f^2-v_i^2`

`implies vf^2=2gh+v^2=2*9.8*20+(0)^2=392`

`impliesv_f^2=392`

`implies v_f=19.799 m/s`

Hence, the velocity on imact is `19.799m/s`.