A ball is projected upward from ground level. After $t$ seconds, its height in feet is a function defined by $f(t)=-16 t^{2}+64 t$. After how many seconds will it reach a height of $48 \mathrm{ft}$ ?
A) $1.5 \mathrm{sec}$ and $3.5 \mathrm{sec}$
B) $1 \mathrm{sec}$ and $3 \mathrm{sec}$
C) The ball never reaches a height of 48 feet.
D) $1 \mathrm{sec}$

Question

Quizplus · Accepted Answer

To find when the ball reaches 48 feet, solve the equation $-16t^2 + 64t = 48$. This simplifies to $-16t^2 + 64t - 48 = 0$. Solving this quadratic equation gives $t = 1$ and $t = 3$.

A Ball Is Projected Upward from Ground Level ttt Seconds, Its Height in Feet Is a Function Defined By Seconds

A Ball Is Projected Upward from Ground Level $t$ Seconds, Its Height in Feet Is a Function Defined By Seconds