Question

A ball is kicked upward with an initial velocity of 56 feet per second. The ball's height h (in feet) can be expressed as a function of time t (in seconds) by the equation h = -16t2 + 56t. How much time does the ball take to return to the ground?

A) 1.75 seconds
B) 2.50 seconds
C) 2.75 seconds
D) 3.50 seconds

Answer 1

D) 3.50 seconds

Explanation:

You are interested in the positive value of t such that h=0. Substituting 0 for h, we get ...

0 = -16t^2 +56t

0 = -16t(t -3.5) . . . . . factored form

The product is zero when the factors are zero. Here, the factor of interest is ...

0 = t-3.5

3.5 = t . . . . . add 3.5 to both sides

The ball takes 3.5 seconds to return to the ground.