Work Energy Theorem Question I cant do

[Little Dump]

I have no clue how to do b, c and especially d.

Thanks

The cable of the 1,800 kg elevator cab in Fig. 8-51 snaps when the cab is at rest at the first floor, where the cab bottom is a distance d = 3.9 m above a cushioning spring whose spring constant is k = 0.14 MN/m. A safety device clamps the cab against guide rails so that a constant frictional force of 3.6 kN opposes the cab's motion. (a) Find the speed of the cab just before it hits the spring. (b) Find the maximum distance x that the spring is compressed (the frictional force still acts during this compression). (c) Find the distance (above the point of maximum compression) that the cab will bounce back up the shaft. (d) Using conservation of energy, find the approximate total distance that the cab will move before coming to rest. (Assume that the frictional force on the cab is negligible when the cab is stationary.)

 

[Little Dump]

ok i got b and c

thanks

but I am still not getting d

any chance you can give me an equation or something?

more hints?

thanks a bunch

 

[enigma]

Post what you've got, LD!

Forum rules, and all...

 

[Little Dump]

for b i got the following


1800(9.81)(3.9) - 3600(3.9+x) = 1/2k(x)^2

im not quite sure if that is completely correct. I think their might need to be an x in the first term so its

1800(9.81)(3.9+x)

and for c

1/2k(x)^2 - 3600h = (1800)(9.81)h

not sure if that is right either but i think it is, just plug in x from b

and for d...

i still got nothing

someone help please!

 

[StephenPrivitera]

Originally posted by Little Dump

and for d...

i still got nothing

You have to have something! Even if you don't have any clue where to go, you should just write things down, even random things, to get you started. Try to think of how you can you what you know to find what you want. Specifically, try to find a formula that contains your unknown. If you know how to find all the other variables, then you're done.
For example, I randomly wrote down W_{net-nonconserv}=[del]E_mechanical. Of course, the nonconservative work is the work done by _____. The mechanical energy is given by _____.

 

[Little Dump]

I got all of them except b now

is my formula for b right?

cuz i get the wrong answer