Question

a ball is projected from the bottom of the 15m high tower in the vertically upwards direction with a speed of 20m/s. at what time it will reach the top of the tower

Answer 1

Answer:

The component of velocity in the vertical-upward direction is,

v=50sin(300)=50×0.5=25m/s

Let the time taken to reach ground from initial position be t sec

The acceleration due to gravity is, g=10m/s2, in the vertical-downward direction.

and the distance traveled is, h=70m, in the vertical-downward direction.

So here, h=−vt+21gt2⟹70=−25t+(0.5×10×t2)

⟹t2−5t−14=0

Solving above quadratic equation, we get t=−2,7

As time is always positive, t=7s