You can put this solution on YOUR website! A projectile is thrown upward at the rate of 42 feet per second from a platform 150 feet high.
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How long does it take to hit ground?
Let t = time in seconds
;
The three parts of this equation are:
Gravity (downward): -16t^2
Velocity up-ward: 42t
Platform ht: 150
:
The height of the ground is 0, find t when the equation = 0:
-16t^2 + 42t + 150 = 0
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Unfortunately, this has to be solved by using the quadratic formula:
a = -16; b = 42; c = 150, find t:
:
:
:
:
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Two solutions:
t = -2.01, we don't want the negative solution
and
t = +4.64375 seconds to hit the ground
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You can check this by substituting 4.64375 for t in the original equation
