Question

A ball is thrown into the air with an upward velocity of 80 feet per second. The function

h = -16t^2 + 80t models the height h, in feet, of the ball at time t, in seconds. When will the ball reach the ground?

after 3 seconds
after 5 seconds
after 6 seconds

Answer 1

after 5 seconds, that is the answer.

Answer 2

5 seconds

B is correct

Explanation:

`h(t)=-16t^2+80t`

where, t is time in seconds, h is height of ball in feet

When ball at ground h must be 0.

Set h=0 and solve for t

`0=-16t^2+80t`

`-16t(t-5)=0`

`t=0,t-5=0`

`t=0,5`

Hence, The ball reach at ground in 5 seconds