Question

Whitney kicks a football off the ground. The height, h , in feet, of the football above the ground after t seconds is given by h ( t ) = − 8 t 2 + 32 t . How many seconds after the football is kicked does it hit the ground for the first time?

Answer 1

after 4seconds

Explanation:

Given the height, h , in feet, of the football above the ground after t seconds expressed by h ( t ) = − 8 t^2 + 32 t, the height of the ball on the ground is 0feet.

Substitute h(t) = 0 into the expression and calculate t;

h ( t ) = − 8 t^2 + 32 t

0 = − 8 t^2 + 32 t

8t² = 32t

8t = 32

Divide both sides by 8

8t/8 = 32/8

t = 4s

Hence the football hits the ground after 4seconds