Solve the problem.
-An object is propelled vertically upward from the top of a 128-foot building. The quadratic function models the ball's height above the ground, s(t), in feet, t seconds after it was thrown. $$s ( t ) = - 16 t ^ { 2 } + 112 t + 128$$ How many seconds does it take until the object finally hits the ground? Round to the nearest tenth of a second if
Necessary.
A) 2 seconds
B) 1.0 seconds
C) 3.5 seconds
D) 8.0 seconds

Question

Quizplus · Accepted Answer

To find when the object hits the ground, set $s(t) = 0$ and solve for $t$. The equation becomes $-16t^2 + 112t + 128 = 0$. Factoring or using the quadratic formula, we find the time $t$ when the object hits the ground. The correct answer, when solved, is approximately 8.0 seconds.

Solve the Problem s(t)=−16t2+112t+128s ( t ) = - 16 t ^ { 2 } + 112 t + 128s(t)=−16t2+112t+128

Solve the Problem $s ( t ) = - 16 t ^ { 2 } + 112 t + 128$