A rock falls from a tower that is $117.6 \mathrm {~m}$ high. As it is falling, its height is given by the formula $h = 117.6 = 4.9 \mathrm { t } 2$, with $t$ in seconds. How many seconds will it take for the rock to hit the ground $( h = 0 )$ ?
A) 10.8 sec
B) 2822.4 sec
C) 10.6 sec
D) 4.9 sec

Question

Quizplus · Accepted Answer

The correct formula should be $h = 117.6 - 4.9t^2$. Setting $h = 0$, we solve $117.6 - 4.9t^2 = 0$, which gives $t^2 = 24$, so $t = \sqrt{24} \approx 4.9$ seconds.

A Rock Falls from a Tower That Is 117.6 m117.6 \mathrm {~m}117.6 m

A Rock Falls from a Tower That Is $117.6 \mathrm {~m}$