Question

Sharon kicks a ball from the ground into the air with an upward velocity of 64 feet per second. The function h = -16t2 + 64t models the height h, in feet, of the ball at time t, in seconds. When will the ball reach the ground again?

A: 1 second after the ball is thrown

B: 2 seconds after the ball is thrown

C: 3 seconds after the ball is thrown

D: 4 seconds after the ball is thrown

Answer 1

the answer would be 4 seconds

Answer 2

When the ball reaches the ground is equal to one of the zeros, or x-intercepts. In order to find the zeros of a function, you need to factor the equation.
y=16x^2+64x
y=-16x(x-4)
The zeros are x=0 and x=4
Therefore the answer is D, after 4 seconds.
Hope this helps!