The height of a golf ball after being hit is described by the function h = - 5t^2 + 20t, where h metres is the height, t seconds after the ball has been hit.

Question

The height of a golf ball after being hit is described by the function h = - 5t^2 + 20t, where h metres is the

height, t seconds after the ball has been hit.

a) what is the maximum height of the ball?

b) how many seconds after impact is the maximum height reached?

c) when does the ball hit the ground?

Answer 1

h = -5t^2 + 20t

h' = -10t + 20 = 0

t= 2 seconds at maximum height

maximum height = 20 meters at 2 seconds

the ball hits the ground when h=0

-5t^2 + 20t = 0

-5t(t -4) = 0

t= 4 seconds when it hits the ground