Solve the problem.
-A rock falls from a tower that is 68.6 m high. As it is falling, its height is given by the formula $h = 68.6 - 4.9 t ^ { 2 }$ with t in seconds. How many seconds will it take for the rock to hit the ground (h =0)?
A) 8 sec
B) 3.7 sec
C) 8.3 sec
D) 960.4 sec

Question

Quizplus · Accepted Answer

To find the time it takes for the rock to hit the ground, set $h = 0$ and solve for $t$: $0 = 68.6 - 4.9t^2$. Rearranging gives $4.9t^2 = 68.6$, and solving for $t$ gives $t = \sqrt{\frac{68.6}{4.9}}$, which approximately equals 3.7 seconds.

Solve the Problem h=68.6−4.9t2h = 68.6 - 4.9 t ^ { 2 }h=68.6−4.9t2

Solve the Problem $h = 68.6 - 4.9 t ^ { 2 }$