# The height in feet of a golf ball hit into the air is given by h= -16t^2 + 64t, where t is the number of seconds elapsed since the ball was hit. How long does it take for the ball to hit the ground?

Jul 11, 2017

After $4$ seconds the the ball will hit the ground.

#### Explanation:

When hitting the ground , $h = 0 \therefore - 16 {t}^{2} + 64 t = 0$ or

$t \left(- 16 t + 64\right) = 0 \therefore$ either $t = 0 \mathmr{and} \left(- 16 t + 64\right) = 0 \therefore 16 t = 64 \mathmr{and} t = 4$

t=0 or t=4 ; t=0 indicates initial point. So $t = 4$ seconds

After $4$ seconds the the ball will hit the ground. [Ans]