SOLUTION: Anobject that is projected straight downward with initial velocity v feet per square travels a distance s=vt+16tsquared,where t=time in seconds. If Ramon is standing on a balcony

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Question 192305: Anobject that is projected straight downward with initial velocity v feet per square travels a distance s=vt+16tsquared,where t=time in seconds. If Ramon is standing on a balcony 84ft above the ground and throws a penny straight down with an initial velocity of 10ft per second,in how many seconds will it reach the ground?
Answer by RAY100(1637) About Me  (Show Source):
You can put this solution on YOUR website!
s=vt+16t^2
84=10t+16t^2
subt 84 both sides
0=16t^2+10t-84
factor
0=2(8t^2+5t-42)
factor bracket using quadratic eqn
a=8, b=5, c=-42
t= (-(5) +- sq rt ( (-5)^2-4 (8) (-42) )/2(8)
t=(-5+- sq rt ( 25 + 1344) )/16
t= (-5 +- sq rt (1369) 0/16
t= (-5 +- 37)/16
t= (-5-37)/16=-2.625 not realistic, neg time
or t= (-5+37)/16= +2
checking
s=vt+16t^2
84=10(2) +16(2^2)=20+62=84 ok