Question

An object at a height of 24 feet is thrown upward with an initial velocity of 8 feet per second. When will the object hit the ground?

Answer 1

We put the acceleration of gravity, the initial velocity and the initial height all together to get our formula for height as a function of time:

y = -16t² + 8t + 24

We want to know when y=0

0 = -16t² + 8t + 24

0 = 2t² - t - 3

0 = (t + 1)(2t - 3)

t= -1 or t=3/2

We reject the negative root.

Answer: 1.5 seconds later