Question

A ball when released from the top of multi storeyed building reaches the bottom in 2s. Find the height of the building. Calculate the velocity of the ball when it reaches the earth.

Answer 1

Hello,

We know the time it takes for the ball to reach the ground, ie., 2s.

Now since we're just dropping the ball freely, we assume only gravity to be acting on the body, ie., g=10m/s^2.

Initial velocity u=0.

Final velocity v=x (say).

Using v-u=gt

t=(v-u)/g

Substituting

2=x/10

x=20ms^-1.

Now, distance (height s) = (1/2)*gt^2

= 1/2*10*4

=20m.

Hope it helps!