The height in feet h of a rocket in flight is given by the formula $h = - 16 t ^ { 2 } + 160 t$ , where t is the time of the flight in seconds. How long will it take for the rocket to hit the ground?
A)11 sec
B)10 sec
C)8 sec
D)12 sec
E)13 sec

Question

Quizplus · Accepted Answer

When the rocket hits the ground, its height will be 0. So we set the formula to 0 and solve for t:
$$-16t^2+160t=0$$
Factor out t:
$$t(-16t+160)=0$$
Simplify:
$$-16t+160=0$$
$$t=10$$
So it will take 10 seconds for the rocket to hit the ground. Answer: B.

The Height in Feet H of a Rocket in Flight h=−16t2+160th = - 16 t ^ { 2 } + 160 th=−16t2+160t

The Height in Feet H of a Rocket in Flight $h = - 16 t ^ { 2 } + 160 t$