# Homework Help: Work and Hooke's Law

1. Mar 4, 2014

### alingy1

1. The problem statement, all variables and given/known data
A vertical spring of negligible mass and spring constant k=1000N/m has a small object of mass M=5.0kg placed on its top. The spring is held compressed by distance of 25 cm from equilibrium position. The spring is released. Find speed of mass at equilibrium position.

2. Relevant equations

W spring=1/2kdeltax^2
W gravity=deltax*5*9.8
Total energy gain of mass=19J
Energy transferred into potential: 12.25J=mgh
Energy transferred into kinetic: 6.75J ---->v=1.64m/s

3. The attempt at a solution

The answer booklet says the answer is 2.76m/s!
Where did I go wrong?

2. Mar 4, 2014

### Staff: Mentor

I don't know. The 19J seems too low. I got about 32 J. You didn't subtract the potential energy change twice, did you?

Chet

3. Mar 4, 2014

### Staff: Mentor

When evaluating this, don't overlook that power of 2.

Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted