Asked by Elle

The cable of an elevator of mass M = 1020 kg snaps when the elevator is at rest at one of the floors of a skyscraper. At this point the elevator is a distance d = 18.4 m above a cushioning spring whose spring constant is k = 6500 N/m. A safety device clamps the elevator against the guide rails so that a constant frictional force of f = 6678 N opposes the motion of the elevator. Find the maximum distance by which the cushioning spring will be compressed.

This is what I did but the answer was wrong!:
Wtotal = (mg- f) 18.4m
Wtotal = 1/2 kx^2
Answered by Quidditch
Your approach looks OK.
Check for any errors in copying the problem or any math errors.
Answered by Elle
Wtotal = [(1020)(9.8)-6678] 18.4
= 61051.2J
61051.2J = 1/2 (6500)x^2
x = 4.33m

STill wrong :( Help
Answered by Quidditch
The displacement of the safety spring has to be considered in the total potential energy of the elevator car.
Answered by Elle
Um are you saying
Wtotal = [(1020)(9.8)-6678] (18.4+x) ?..
In that case, I did the quadratic and got x=17.33m, but still wrong answer :( argg
Answered by Quidditch
For the roots of the quadratic I got
+4.875
-3.854
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