SOLUTION: A Ball is thrown upward from a height of 15 ft. with an initial upward velocity of 5 ft a sec. Use the formula h=-16t squared+vt+s to find out how long it will take for the ball to

Question 440852: A Ball is thrown upward from a height of 15 ft. with an initial upward velocity of 5 ft a sec. Use the formula h=-16t squared+vt+s to find out how long it will take for the ball to hit the ground?
Found 2 solutions by Alan3354, stanbon:
Answer by Alan3354(69443) (Show Source): You can put this solution on YOUR website!
h(t) = -16t^2 + 5t + 15
It impacts when h=0
-16t^2 + 5t + 15 = 0

Solved by pluggable solver: SOLVE quadratic equation (work shown, graph etc)

Quadratic equation (in our case ) has the following solutons:

For these solutions to exist, the discriminant should not be a negative number.

First, we need to compute the discriminant : .

Discriminant d=985 is greater than zero. That means that there are two solutions: .

Quadratic expression can be factored:

Again, the answer is: -0.824522176654701, 1.1370221766547. Here's your graph:

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Ignore the negative solution
t = 1.137 seconds
Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
A Ball is thrown upward from a height of 15 ft. with an initial upward velocity of 5 ft a sec. Use the formula h=-16t squared+vt+s to find out how long it will take for the ball to hit the ground?
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h=-16t squared+vt+s
h(t) = -16t^2+5t+15
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Height is zero when the ball hits the ground:
---
Solve: -16t^2+5t+15 = 0
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Use Quadratic Formula:
t = [-5 +- sqrt(25-4*-16*15)]/(-32)
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t = [-5 +- sqrt(985)]/(-32)
---
Positive solution:
t = [-5-31.38]/(-32)
t = 1.1370 seconds
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Cheers,
Stan H.

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