SOLUTION: The only part of the height equation we have not discussed is the constant. You have probably noticed that the constant is always equal to the initial height of the ball (80 m in o

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Question 78382: The only part of the height equation we have not discussed is the constant. You have probably noticed that the constant is always equal to the initial height of the ball (80 m in our previous exercises.) Now let’s have you develop a height equation. A ball is thrown upward from the roof of a building 100 m tall with an initial velocity of 20m/s.
h = -5t^2 + 20t +100
37. Science and medicine. How long does it take the ball to fall back to the ground?
Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
h = -5t^2 + 20t +100
37. Science and medicine. How long does it take the ball to fall back to the ground?
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The height is zero when the ball is back on the ground.
Solve -5t^2+20t+100=0
t^2-4t-20=0
t=[4+-sqrt(16-4*-20)]/2
t=[4+-sqrt(96)]/2
t=[4+-4sqrt6)[/2
t=[2+-2sqrt6]
The positive answer is:
t=2+2sqrt6 = 6.9 seconds
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graph%28400%2C300%2C0%2C10%2C-2%2C150%2C-3x%5E2%2B20x%2B100%29
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Cheers,
Stan H,
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Cheers,
Stan H.