Question

A ball is thrown vertically upwards with and velocity of 20 metre per second from the top of a multi storey building the height of the point where the ball is thrown is 25 metre from the ground how long will it be before the ball hits the ground at 1 G equals to 10 metre per second square

Answer 1

(a)

H = u²/(2g)

H = 20²/(2×10)

H = 20 m

The ball will reach 20 m high from the point of projection.

It reaches 20 + 20.5 = 40.5m high from the ground.

(b)

t1 = 2u/g

t1 = 2×20/10

t1 = 4 seconds

If v is the velocity with which it hits the ground then,

v = √(u² + 2aS)

v = √(20² + 2×10×25)

v = 30 m/s

v = u + at

t2 = (v - u)/g

t2 = (30 - 20)/10

t2 = 1 second

Time taken for it to hit the ground = t1 + t2

= 4 + 1

= 5 seconds

Note: I took g = 10m/s².

Answer 2

Explanation:

Please see the attachment

hope that helped