# physics

posted by
**rebecca** on
.

a boy who is 1.5m tall throws a ball into the air the ball attains a height a of 3m above the boy's head and then falls back to the ground the boy's hand was 1.2 m above the ground when he released the ball

how long does it take to reach it's maximum height?

what is the initial velocity , final velocity off the ball

initial height= 2.7m

max height=4.5m

I would do this with energy. You know the initial potential energy.... mghi, and the final potential energy mg*hmax. The difference represents the kinetic energy of the ball initally 1/2 m v^2

The final kinetic energy is equal to mg*hmax