SOLUTION: An angry construction worker throws his wrench downward form a height of 128ft with an initial velocity of 32ft per second. The height of the wrench above the ground after t second

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Question 203756This question is from textbook
: An angry construction worker throws his wrench downward form a height of 128ft with an initial velocity of 32ft per second. The height of the wrench above the ground after t seconds is given by S(t)= -16t^2-32t+128. This question is from textbook

Answer by Earlsdon(6294) About Me  (Show Source):
You can put this solution on YOUR website!
Er...what's the question?
Could it be that you want to know when the wrench hits the ground (or an unfortunate passer-by)?
Let's assume that it is!
Given:
S%28t%29+=+-16t%5E2-32t%2B128 the wrench hits the ground when its height, S = 0.
0+=+-16t%5E2-32t%2B128 Rearrange this to look like:
-16t%5E2-32t%2B128+=+0 Factor out a -16 to ease the calculations a bit.
-16%28t%5E2%2B2t-8%29+=+0 Note the changes in the signs! Applying the zero product rule, we get:
t%5E2%2B2t-8+=+0 Factor this quadratic equation.
%28t-2%29%28t%2B4%29+=+0 from which we get:
t+=+2 or cross%28t+=+-4%29 Discard the negative solution as the time, t, should be a positive value.
The wrench hits the ground in 2 seconds.