If a projectile is launched upward from the ground with an initial velocity of 64.5 feet per second, its height $h$ in feet $t$ seconds later is given by the function $h(t)=-16 t^{2}+64.5 t$. After how many seconds does the projectile land on the ground?
A) 4.0 seconds
B) 2.0 seconds
C) 8.1 seconds
D) 0.2 seconds

Question

Quizplus · Accepted Answer

To find when the projectile lands, set $h(t) = 0$ and solve for $t$: $-16t^2 + 64.5t = 0$. Factoring out $t$, we get $t(-16t + 64.5) = 0$, which gives $t = 0$ (launch time) and $t = 4.0$ seconds (landing time).

If a Projectile Is Launched Upward from the Ground with an Initial