A rock falls from a tower that is 480 feet high. As it is falling, its height is given by the function $h(t)=-16 t^{2}+480 t$. How many seconds will it take for the rock to land on the ground?
A) 21.5 seconds
B) 14,400 seconds
C) 21.9 seconds
D) 5.5 seconds

Question

Quizplus · Accepted Answer

To find the time it takes for the rock to hit the ground, we set $h(t) = 0$ and solve for $t$. This gives us the equation $0 = -16t^2 + 480$. Dividing through by -16 gives $t^2 = 30$, and taking the square root gives $t = \sqrt{30}$, which is approximately 5.5 seconds.

A Rock Falls from a Tower That Is 480 Feet h(t)=−16t2+480th(t)=-16 t^{2}+480 th(t)=−16t2+480t

A Rock Falls from a Tower That Is 480 Feet $h(t)=-16 t^{2}+480 t$