SOLUTION: A toy rocket is shot vertically into the air from a launching pad 9 feet above the ground with an initial velocity of 80 feet per second. The height h, in feet, of the rocket above

Algebra ->  Coordinate Systems and Linear Equations  -> Linear Equations and Systems Word Problems -> SOLUTION: A toy rocket is shot vertically into the air from a launching pad 9 feet above the ground with an initial velocity of 80 feet per second. The height h, in feet, of the rocket above      Log On


   

Question 1154333: A toy rocket is shot vertically into the air from a launching pad 9 feet above the ground with an initial velocity of 80 feet per second. The height h, in feet, of the rocket above the ground at t seconds after launch is given by the function h(t)=-16t^2+80t+9. How long will it take the rocket to reach its maximum height?
Found 2 solutions by mananth, ikleyn:
Answer by mananth(16946) About Me  (Show Source):
You can put this solution on YOUR website!
h(t) = -16t^2 + 80t + 9.
compare with equation ax%5E2%2Bbx%2Bc=0
a=-16, b=80 c =9
time to go to height h = -b%2F2a
=(80/32)= 2.5 s

time to go maximum height is t = = = = 2.5 seconds.

The maximum height you can get by substituting this value t= 3.5 in the formula
h(t) = -16t^2 + 80t + 9
h(2.5) = -16*2.5^2 + 80*2.5 + 9.
h =109m

Answer by ikleyn(52787) About Me  (Show Source):
You can put this solution on YOUR website!
.

The correct answer for the maximum height is 109 feet     ( not meters (!) )