(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

A 4000 elevator breaks off and falls from rest 12 ft above the surface of a relaxed spring. The elevator has a safety system so that the elevator will always experience a frictional force with a constant magnitude of 1000 lb. The spring constant k is equal to 10 000 lb/ft

a) find velocity just before it hits the spring

b) how much does the elevator compress the spring before it stops?

2. Relevant equations

3. The attempt at a solution

I solved part a and for 24 ft/s. For part b, I tried using this equation:

sum of conservative forces work + work of friction = change in K

work of gravity + work of spring + work of friction = change in K

then it would be

-ky^2 + (4000 - 1000)y + 1/2mv^2 = 0

because change in K = 0 - K-initial..

plugging in the rest, it should be solvable. But it didn't work out. The reasoning seems fine? what happened? thanks

**Physics Forums | Science Articles, Homework Help, Discussion**

Dismiss Notice

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Homework Help: Energy question, displacement of a spring

**Physics Forums | Science Articles, Homework Help, Discussion**