I hate when I think I got the whole concept right only to get the answer wrong! I really hope it is a simple mis-calculation but I triple-checked all my work.
(a For the elevator of Example 7.9, what is the speed of the elevator after it has moved downward 1.00 m from point 1. (b)When the elevator is 1m below point 1, what is its acceleration? [I'm only concerned with part a for this problem, its the part that gives me trouble]
Here is all the information you need to know from example 7.9
m = 2000kg (19600 N)
initial velocity = 4 m/s
k = 10600 N/m
friction = 17000 N
Work of friction = -34000J
I set initial height to be 0m and height when compressed 1m to be -1m.
so then initial gravitational PE & initial elastic PE go to 0
[tex]16000J - 34000J = 1000 kg v^2 -19600J + 5300 J[/tex]
since velocity is pointing down I put a - sign in front of it and I also add a couple terms.
[tex]1600J-34000 J= 1000kg (- v^2) - 14300 J[/tex]
Edit: Corrected 10000kg to 1000 kg for 1/2m, but still getting a wrong answer.