Question 449709
if an object is projected upward with an initial velocity off 64 ft per sec from a height of 336 feet then its height t sec after it is projected is defined by the equation h= -16t^2 + 64 t + 336. how many sec after it is projected will it hit the ground?
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When object hits the ground its height will be=0
0= -16t^2 + 64 t + 336
-16t^2 + 64 t + 336=0
divide by -16
t^2-4t-21=0
(t-7)(t+3)=0
t-7=0
t=7 seconds
t+3=0
t=-3 (reject, t≥0)
ans:
object will hit the ground 7 seconds after it is projected.