SOLUTION: A ball is thrown upward from the top of a 240 foot building. The ball is 256 feet above ground level a fter 1 second, and it reaches ground level in 5 seconds. the height above gr

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Question 724176: A ball is thrown upward from the top of a 240 foot building. The ball is 256 feet above ground level a fter 1 second, and it reaches ground level in 5 seconds. the height above ground is a quadratic function of the time after the ball is thrown. Write the equation of this function.
Found 2 solutions by Alan3354, josmiceli:
Answer by Alan3354(69443) About Me  (Show Source):
You can put this solution on YOUR website!
A ball is thrown upward from the top of a 240 foot building. The ball is 256 feet above ground level a fter 1 second, and it reaches ground level in 5 seconds. the height above ground is a quadratic function of the time after the ball is thrown. Write the equation of this function.
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It's the common formula for projectiles on Earth.
h(t) = -16t^2 + vt + h, h in feet
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h(1) = -16 + v + 240 = 256
v = 32 ft/sec (the upward speed at launch)
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h(t) = -16t^2 + 32t + 240 is the equation
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h(5) = -400 + 160 + 240 = 0 confirms impact at t = 5 seconds

Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
The form of the equation is:
+h+=+-a%2At%5E2+%2B+v%2At+%2B+h%5B0%5D+
given:
+h%5B0%5D+=+240+ ft
When +t+=+1+, +h+=+256+
When +t+=+5+, +h+=+0+
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+256+=+-a%2A1%5E2+%2B+v%2A1+%2B+240+
(1) ++-a+%2B+v++=+16+
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+0+=+-a%2A5%5E2+%2B+v%2A5+%2B+240+
(2) +25a+-+5v+=+240+
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(2) +5a+-+v+=+48+
Add (1) and (2)
(1) ++-a+%2B+v++=+16+
(2) +5a+-+v+=+48+
+4a+=+64+
+a+=+16+
and, since
(1) ++-a+%2B+v++=+16+
(1) ++-16+%2B+v++=+16+
(1) +v+=+32+
The equation is:
+h+=+-16t%5E2+%2B+32t+%2B+240+
Here's the plot:
+graph%28+400%2C+400%2C+-1%2C+6%2C+-20%2C+280%2C++-16x%5E2+%2B+32x+%2B+240+%29+