Sandra throws an object straight up into the air with an initial velocity of 38 ft/s from a platform that is 30 ft above the ground. Use the formula h (t) = -16t2+v0t+h0, where v0 is the initial velocity and h0 is the initial height. How long will it take for the object to hit the ground?

A. 1 s

B. 2 s

C. 3 s

D. 4 s

The answer is C.

Step-by-step explanation:

Given formula h (t) = -16t2+v0t+h0, where v0 is the initial velocity and h0 is the initial height.

In this case, the initial postion is a platform 30ft above ground so h0=+30

The initial velocity is 38 ft/s straight up into the air so v0=+38

h (t) = -16t2+38t+30

When the object hits the ground, h=0.

h=-16t2+38t+30=0

Simplifying 8t2-19t-15=0

(8t+5) (t-3) = 0

t=-5/8 or 3

As time cannot be - ve, t=3s. The answer is C.