SOLUTION: Fireworks are shot upward with an intial velocity of 125 feet per second from a paltform 3 feet abouve the ground. use the model h= -16t squared + vt + s to find how long it will

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Question 445089: Fireworks are shot upward with an intial velocity of 125 feet per second from a paltform 3 feet abouve the ground. use the model h= -16t squared + vt + s to find how long it will take the rocket to hit the ground?
Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
You can put this solution on YOUR website!
Fireworks are shot upward with an intial velocity of 125 feet per second from a platform 3 feet abouve the ground.
Use the model h = -16t squared + vt + s to find how long it will take the rocket to hit the ground?
:
In this problem: v = 125, s = 3, h = 0, (h = 0 when it hits the ground)
:
-16t^2 + 125t + 3 = 0
Use the quadratic formula to solve this:
x+=+%28-b+%2B-+sqrt%28+b%5E2-4%2Aa%2Ac+%29%29%2F%282%2Aa%29+
In this equation: x=t; a=-16, b=125, c=3
t+=+%28-125+%2B-+sqrt%28125%5E2-4%2A-16%2A3+%29%29%2F%282%2A-16%29+
:
t+=+%28-125+%2B-+sqrt%2815625-%28-192%29+%29%29%2F%28-32%29+
:
t+=+%28-125+%2B-+sqrt%2815625+%2B+192+%29%29%2F%28-32%29+
:
t+=+%28-125+%2B-+sqrt%2815817%29%29%2F%28-32%29+
Two solutions
t+=+%28-125+%2B+125.765655%29%2F%28-32%29+
t+=+%28.765655%29%2F%28-32%29+
t = -.023926
and
t+=+%28-125+-+125.765655%29%2F%28-32%29+
t+=+%28-250.765655%29%2F%28-32%29+
t = +7.8364 sec, the reasonable solution, for the rocket to hit the ground