Question

A ball is gently dropped from the top of a building, reaches the ground in 2
seconds. If the ball accelerate uniformly at the rate of 10 m/s 2
, find

i) The height of the building.
ii) Velocity of the ball just before it strikes the ground.

Answer 1

Correct option is

A

20 m/s, 2 s

Given, initial velocity of ball, u=0

Final velocity of ball, v=?

Distance through which the balls falls, s=20m

Acceleration a=10ms−2

Time of fall, t=?

We know

v2−u2=2as

or v2−0=2×10×20=400 or v=20ms−1

Now using v=u+at we have

20=0+10×t or t=2s