# Homework Help: Stretching distance of spring

1. Jan 13, 2013

### firezap

1. The problem statement, all variables and given/known data
See image attachment

2. Relevant equations
Fs = kx
Es = 1/2 kx^2
ET1 = ET2 which is Eg1 + Ek1 + Es1 + work applied = Eg2 + Ek2 + Es2 + friction

3. The attempt at a solution

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2. Jan 13, 2013

### Staff: Mentor

This is a force/equilibrium problem, not an energy problem.

A hint to start you off: If you look at diagram I and imagine the spring cut into three pieces, how much does each piece stretch?

3. Jan 13, 2013

### firezap

each piece will stretch 1 cm

4. Jan 13, 2013

### Staff: Mentor

Good. So now you know that the weight of the complete rod will stretch one of the spring pieces by 1 cm. How much will the weight of 1/3 of the rod stretch one of those spring pieces?

Use this reasoning to figure out how much each spring stretches in diagram II.

5. Jan 13, 2013

### firezap

1/3 x 1cm = 1/3cm
is it 1/3cm + 2/3cm + 3/3cm = 2cm

6. Jan 13, 2013

Good!