A rock falls from a tower that is 208 feet high. As it is falling, its height is given by the formula $h = 208 - 16 t { } ^ { 2 }$. How many seconds (in tenths) will it take for the rock to hit the ground $( h = 0 )$ ?
A) 3.6 sec
B) 13.9 sec
C) 14.4 sec
D) 2704 sec

Question

Quizplus · Accepted Answer

To find the time it takes for the rock to hit the ground, set $h = 0$ and solve for $t$: $0 = 208 - 16t^2$. Solving for $t^2$ gives $t^2 = 13$, and taking the square root gives $t = \sqrt{13} \approx 3.6$ seconds.

A Rock Falls from a Tower That Is 208 Feet h=208−16t2h = 208 - 16 t { } ^ { 2 }h=208−16t2

A Rock Falls from a Tower That Is 208 Feet $h = 208 - 16 t { } ^ { 2 }$