Question

A ball is thrown upward from a building. The height h after t seconds is determined from the quadratic equation h ( t ) = t^2−8t−48 . Find after how many seconds the ball will touch the ground.

Answer 1

12 seconds.

Explanation:

When the ball hits the ground h(t) = 0:

t^2 - 8t - 48 = 0

(t - 12)(t + 4) = 0

t = 12, -4 ( we ignore the negative).

The required time = 12 seconds.