SOLUTION: an object that is projected straight downward with an initial velocity of v per second travels a distance s = vt + 9t^2, where t=time in seconds. if dan is standing on a balcony 17

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Question 452889: an object that is projected straight downward with an initial velocity of v per second travels a distance s = vt + 9t^2, where t=time in seconds. if dan is standing on a balcony 176 feet above the ground and throws a penny straight downward with an intial velocity of 8 feet per second, in how many seconds will it reach the ground?
Answer by lwsshak3(11628) About Me  (Show Source):
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an object that is projected straight downward with an initial velocity of v per second travels a distance s = vt + 9t^2, where t=time in seconds. if dan is standing on a balcony 176 feet above the ground and throws a penny straight downward with an intial velocity of 8 feet per second, in how many seconds will it reach the ground?
..
When the object reaches the ground it will have traveled 176 feet
176=8t+9t^2
9t^2+8t-176=0
solve by following quadratic formula
..
x+=+%28-b+%2B-+sqrt%28+b%5E2-4%2Aa%2Ac+%29%29%2F%282%2Aa%29+
..
a=9, b=8, c=-176
t=[-8ħsqrt(8^2-4*9*-176)]/2*9
t=[-8ħsqrt(6400)]/18
t=(-8ħ80)/18
t=72/18=4 sec
or
t=-88/18=-4.88..(reject, time≥0)
ans:
The object wll reach the ground in 4 seconds.