Question

A rock is thrown straight upward with an initial velocity of 20 m/s where the downward acceleration due to gravity is -10 m/s^2. How long is the ball in the air before it returns to the thrower's hand?

Answer 1

4 seconds

Step-by-step explanation:

Given:

Δy = 0 m

v₀ = 20 m/s

a = -10 m/s²

Find: t

Δy = v₀ t + ½ at²

0 m = (20 m/s) t + ½ (-10 m/s²) t²

0 = 20t − 5t²

0 = 5t (4 − t)

t = 4