SOLUTION: Throwing a wrench: An angry contruction worker throws his wrench downward from a height of 128 ft with an initial velocity of 32 feet per second. The height of the wrench above th

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Question 201852: Throwing a wrench: An angry contruction worker throws his wrench downward from a height of 128 ft with an initial velocity of 32 feet per second. The height of the wrench above the ground after t seconds is given by
S(t) = -16r - 32r + 128
A. What is the height of the wrench after 1 second?
B. How long does it take for the wrench to reach the ground?
Found 2 solutions by Alan3354, Earlsdon:
Answer by Alan3354(69443) About Me  (Show Source):
You can put this solution on YOUR website!
An angry contruction worker throws his wrench downward from a height of 128 ft with an initial velocity of 32 feet per second. The height of the wrench above the ground after t seconds is given by
S(t) = -16r - 32r + 128
A. What is the height of the wrench after 1 second?
B. How long does it take for the wrench to reach the ground?
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You have r's in a function that's S(t) ??
----------------
h(t) = -16t^2 -32t + 128
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A. h(1) = -16 - 32 + 128
h(1) = 80 feet
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B. -16t^2 - 32t + 128 = 0
t^2 + 2t - 8 = 0
(t+4)*(t-2) = 0
t = 2 seconds to reach the ground

Answer by Earlsdon(6294) About Me  (Show Source):
You can put this solution on YOUR website!
First, it appears as though that you have a little mix-up in the independent variable (t) in the formula. It should be:
S%28t%29+=+-16t%5E2-32t%2B128
A) What is the height of the wrench after 1 second?
Set t = 1 and solve for S.
S%281%29+=+-16%281%29%5E2-32%281%29%2B128
S%281%29+=+-16-32%2B128
S%281%29+=+-48%2B128
highlight%28S%281%29+=+80%29feet.
B) How long does it take for the wrench to reach the ground?
Here, you are looking for the time, t, at which S(t) is zero (ground-level), so set S(t) = 0 and solve for t.
-16t%5E2-32t%2B128+=+0 To simplify the calculations a bit, divide both sides by -16.
t%5E2%2B2t-8+=+0 Factor the trinomial.
%28t%2B4%29%28t-2%29+=+0 Now apply the zero product rule.
t%2B4+=+0 or t-2+=+0 so then...
t+=+-4 or t+=+2 Discard the negative solution as time is a positive value.
highlight%28t+=+2%29seconds.