Solve the problem.
-A ball is thrown vertically upward from the top of a building 144 feet tall with an initial velocity of 128 feet per second. The distance s (in feet) of the ball from the ground after t seconds is After how $$s = 144 + 128 t - 16 t ^ { 2 }$$ many seconds does the ball strike the ground?
A) 9 sec
B) 145 sec
C) 11 sec
D) 8 sec

Question

Quizplus · Accepted Answer

To find when the ball strikes the ground, set $s = 0$ and solve for $t$: $0 = 144 + 128t - 16t^2$. This is a quadratic equation in the form of $at^2 + bt + c = 0$, where $a = -16$, $b = 128$, and $c = 144$. Solving this equation using the quadratic formula or factoring (if possible) will give the time $t$ when the ball hits the ground. Factoring or using the quadratic formula gives $t = 9$ seconds as the positive solution relevant to the context of the problem.

Solve the Problem s=144+128t−16t2s = 144 + 128 t - 16 t ^ { 2 }s=144+128t−16t2

Solve the Problem $s = 144 + 128 t - 16 t ^ { 2 }$