Question

A ball thrown vertically upwards from the top of a building of height 80 m returns to the earth after 10 s. What is the velocity of the projection? Also g may be taken as 9.8 m/s2 .

Answer 1

So, the time taken by the ball to reach its maximum height is t1 = 10 s / 2 = 5 s.

The initial velocity (u) of the ball can be calculated using the first equation of motion:

u = v + gt

where:

v is the final velocity (which is 0 at the maximum height),

g is the acceleration due to gravity (9.8 m/s²), and

t is the time taken to reach the maximum height.

Substituting the given values:

u = 0 + 9.8 m/s² * 5 s = 49 m/s

So, the velocity of projection of the ball is 49 m/s.

I hope this helps!