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## Homework Statement

A particle (4m) is suspended from a fixed point by a spring of stiffness k and natural length l

_{0}. An identical 2nd spring is attached to this particle, and a mass (3m) is attached to its end. The system hangs vertically in equilibrium.

Take the datuim of P.E. a in each spring to be the natural length of that spring.

http://img176.imageshack.us/img176/2653/2springsytem.jpg [Broken]

Write down the an equation for the energy stored in the two springs.

## Homework Equations

## The Attempt at a Solution

Spring 1, exerts force

**H**

_{1}=k(x

_{1}-l

_{0})

**i**

it supports both particles so

**W**

_{1}=7mg

**i**

Spring 2, exerts force

**H**

_{2}=k(x

_{2}-l

_{0})

**i**

it supports only the lower particle so

**W**

_{2}=3mg

**i**

The energy function U(x) = - [tex]-\int(F(x)) dx[/tex]

I dont know how to proceed: Should I be integrating 2 equations for the force? Don't I need 'x' in F(x) to be the same in both cases? Have I just got myself in a muddle and am thinking about this all the wrong way?

Any help appreciated.

## Homework Statement

## Homework Equations

## The Attempt at a Solution

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