Solve the problem.
-A projectile is thrown upward so that its distance above the ground after $t$ seconds is $h = - 14 t ^ { 2 } + 560 \mathrm { t }$. After how many seconds does it reach its maximum height?
A) $28 \mathrm { sec }$
B) $40 \mathrm { sec }$
C) $14 \mathrm { sec }$
D) $20 \mathrm { sec }$

Question

Quizplus · Accepted Answer

The maximum height is reached at the vertex of the parabola described by the quadratic equation $h = -14t^2 + 560t$. The vertex occurs at $t = -\frac{b}{2a}$, where $a = -14$ and $b = 560$. Calculating gives $t = \frac{560}{28} = 20$ seconds.

Solve the Problem ttt Seconds Is h=−14t2+560th = - 14 t ^ { 2 } + 560 \mathrm { t }h=−14t2+560t

Solve the Problem $t$ Seconds Is $h = - 14 t ^ { 2 } + 560 \mathrm { t }$