Question

Suppose a toy rocket is launched vertically upward from ground level with an initial velocity of 128 feet per second. If air resistance is ignored, the rocket's h height after t seconds is given by the equation h = ?16t2 +128t. How long will the rocket's flight last?

Answer 1

Answer: Yup it 8 second

Answer 2

8 sec

Explanation:

h= -16t² +128t

how many seconds will go by before the rocket's flight last.

That means we need to find time 't' when the rocket's height h(t) = 0

Therefore,

0= -16t² +128t

Solving for 't'

0 = t(-16t + 128)

0 = t OR 0 = -16t + 128

0 = t OR -128 = -16t

0 = t OR -128/-16 = t

0 = t OR 8 = t

t=0 is not possible because this would mean that rocket hasn't left the ground.

Thus, the rocket's flight will last for 8 sec.