Question

A Harvard University student dropped one of his books from a height of 15 meters off the ground. How long will it take for the book to hit the ground in seconds?

gravity = 9.807 m/s²

Answer 1

1.74901 seconds

Explanation:

The formula for free fall from height x is:

x (m) = 1/2 • g (m/s^2) • t^2 (s^2)

The time t (s) for free fall from height x (m) is:

t (s) = √[2 • x (m) / g (m/s^2)]

So when height x = 15 m,

t (s) = √[2 • 15 (m) / 9.807 (m/s^2)] = 1.74901