document.write( "Question 88682: Suppose you shoot an arrow straight up at a speed of 60 miles per hour when it leaves the bow. From the laws of physics it is possible to deduce that t seconds after leaving the bow the height of the arrow from the ground (in feet) is:\r
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\n" ); document.write( "\n" ); document.write( "h = -16t2 + 88t + 7\r
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\n" ); document.write( "\n" ); document.write( "a. How fast is 60 miles per hour in feet per second?\r
\n" ); document.write( "\n" ); document.write( "b. How high is the arrow 2 seconds after being shot?\r
\n" ); document.write( "\n" ); document.write( "c. About how high does the arrow go before it starts falling back to earth?\r
\n" ); document.write( "\n" ); document.write( "d. When does it hit the ground?\r
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Algebra.Com's Answer #64567 by ankor@dixie-net.com(22740)\"\" \"About 
You can put this solution on YOUR website!
Suppose you shoot an arrow straight up at a speed of 60 miles per hour when it leaves the bow. From the laws of physics it is possible to deduce that t seconds after leaving the bow the height of the arrow from the ground (in feet) is:
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\n" ); document.write( "h = -16t^2 + 88t + 7
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\n" ); document.write( "a. How fast is 60 miles per hour in feet per second?
\n" ); document.write( "60 mph is 1 mi per minute
\n" ); document.write( "Then 5280/60 = 88 ft/sec
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\n" ); document.write( "b. How high is the arrow 2 seconds after being shot?
\n" ); document.write( "Substitute 2 for t:
\n" ); document.write( "-16(2^2) + 88(2) + 7 =
\n" ); document.write( "-16(4) + 176 + 7
\n" ); document.write( "-64 + 176 + 7 = 119 ft
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\n" ); document.write( "c. About how high does the arrow go before it starts falling back to earth?
\n" ); document.write( "Find the axis of symmetry: x = -b/(2a); in this equation: a=-16; b=88
\n" ); document.write( "t = -88/(2*-16)
\n" ); document.write( "t = -88/-32
\n" ); document.write( "t = +2.75 sec
\n" ); document.write( "Find the vertex, which is the max in this problem, substitute 2.75 for t
\n" ); document.write( "h = -16(-2.75^2) + 88(2.75) + 7
\n" ); document.write( "h = -16(7.5625) + 242 + 7
\n" ); document.write( "h = -121 + 242 + 7
\n" ); document.write( "h = 128 ft is max height, begins falling to earth from there (in 2.75 sec)
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\n" ); document.write( "d. When does it hit the ground?
\n" ); document.write( "The height of the ground is 0 so we have:
\n" ); document.write( "-16t^2 + 88t + 7 = 0
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\n" ); document.write( "Have to use the quadratic formula to find t:
\n" ); document.write( "\"t+=+%28-b+%2B-+sqrt%28+b%5E2-4%2Aa%2Ac+%29%29%2F%282%2Aa%29+\"
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\n" ); document.write( "\"t+=+%28-88+%2B-+sqrt%28+88%5E2+-+4+%2A-16+%2A+7+%29%29%2F%282%2A-16%29+\"
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\n" ); document.write( "Solve this you should get a positive solution of:
\n" ); document.write( "t ~ 5.58 sec to reach the ground\r
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