Question

Sarah throw a ball straight up in the air with initial velocity of 19.62m/s. how long will the ball be in the air

Answer 1

Here Sarah projected the ball upwards by speed

$v_i = 19.62 m/s$

here the acceleration is due to gravity

$a = 9.81 m/s^2$

now when ball again lends on the ground the displacement of ball will be zero

$\delta y = v_y * t + \frac{1}{2} at^2$

$0 = 19.62 t - \frac{1}{2}9.81*t^2$

by solving above equation

$t = 4 s$

so it will take 4 s to reach back on ground