SOLUTION: The formula h=-16t^2+vt gives the height h in feet of an object after t seconds when it is shot upward into the air with a velocity v in feet per second. After how many seconds wil

Algebra ->  Percentage-and-ratio-word-problems -> SOLUTION: The formula h=-16t^2+vt gives the height h in feet of an object after t seconds when it is shot upward into the air with a velocity v in feet per second. After how many seconds wil      Log On


   

Question 436971: The formula h=-16t^2+vt gives the height h in feet of an object after t seconds when it is shot upward into the air with a velocity v in feet per second. After how many seconds will an object hit the ground if it is shot upward with an initial velocity of 240 feet per second?

Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
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The formula h=-16t^2+vt gives the height h in feet of an object after t seconds
when it is shot upward into the air with a velocity v in feet per second.
After how many seconds will an object hit the ground if it is shot upward with
an initial velocity of 240 feet per second?
:
Replace h with 0 and v with 240, write the equation:
-16t^2 + 240t = 0
Simplify and change the sign, divide by -8
2t^2 - 30t = 0
Factor
t(2t - 30) = 0
Two solutions
t = 0 (at ground level initially)
and
2t = 30
t = 15 sec to hit the ground
:
:
Check this in the original equation
-16(15^2) + 240(15) =
-16(225) + 3600 = 0