Question

a ball is thrown vertically upwards with velocity of 25 m/s from the top of Tower of height 30m. how long it will take to travel before it hits the ground? g=10m/s^2

Answer 1

H = u²/(2g)
H = 25²/(2×10)
H = 31.25 m

The ball will reach 31.25 m high from the point of projection.
It reaches 30 + 31.25 = 61.25m high from the ground.

t1 = 2u/g
t1 = 2×25/10
t1 = 5 seconds

If v is the velocity with which it hits the ground then,
v = √(u² + 2aS)
v = √(25² + 2×10×30)
v = 35 m/s

v = u + at
t2 = (v - u)/g
t2 = (35 - 25)/10
t2 = 1 second

Time taken for it to hit the ground = t1 + t2
= 5 + 1
= 6 seconds