# Homework Help: Potential Energy of a spring

1. Nov 17, 2009

### xshezsciencex

A certain spring exerts a restoring force F{sub x}(x)= -alpha x - beta x^2 if it is stretched or compressed, where alpha= 60N/m and beta=18N. The mass of the spring is negligible.

How would I : (a) Find the potential energy function U(x) for the spring. Let U=0 when x=0. (b) An object with mass, m = 0.900kg on a frictionless, horizontal surface is attached to this spring, pulled a distance 1.00m to the right to stretch the spring and released. What is the speed of the object when it is 0.500m to the right of the equilibrium position? (c) Use Newtonian dynamics to find the speed at this position. (d) What is the instantaneous power when x= 0.500m?

2. Nov 17, 2009

### tiny-tim

Welcome to PF!

Hi xshezsciencex! Welcome to PF!

Hint: potential energy is (minus) work done = -∫ … ?

3. Nov 17, 2009

### xshezsciencex

im even more confused >_<

4. Nov 17, 2009

### ideasrule

Are you familiar with calculus, or with the equation F=-dU/dx where U is potential energy?