Question

A stone thrown from the top of a building is given an initial velocity of 20.0 m/s straight upward. The stone is launched 50.0 m above the ground Determine the time at which the stone reaches its maximum height.

Answer 1

Given:

$v_0=20.0\:\rm m/s$

$g=9.81\:\rm m/s^2$

$t-?$

At the highest point the stone is at rest, hence

$$v=v_0-gt=0$$

The time of motion

$$t=v_0/g=20.0/9.81=2.04\:\rm s$$