Does the potential energy of a spring do work on the both

• x86
In summary, when modeling the system of two boxes with a spring attached, the conservation of energy equation can be used to account for the changes in kinetic and potential energy. However, the potential energy of the spring can be confusing as it also affects both blocks upon release. Based on personal experience, a spring attached to a fixed wall will push a block faster than a spring attached to another free block. This suggests that some of the energy is used to push both blocks in the latter case. The formula for potential energy, 1/2kx^2, remains the same in both scenarios.
Suppose we have two boxes, A and B with different masses, the spring is fixed to block A.

Then we take block B and press it against block A so that the spring compresses.

Afterwards, we let go of both boxes.

If we were to model this using the conservation of energy, then it is known that

(KE of A)1 + (KE of B)1 + (PE of spring)1= (KE of A)2 + (KE of B)2 + (PE of spring)2

0 + 0 + (PE of spring)1= (KE of A)2 + (KE of B)2 + 0

But one thing is confusing me. That is, the potential energy of the spring.

I know that upon release, it will do positive work on block B. But won't it also do positive work on block A?

Doing an experiment, when I push two masses together with a spring,with the spring attached to one box (a pen spring) both boxes go flying both ways.

Surely this affects the potential energy?

So how do I account for this potential energy?Should it be double, or what?

Last edited:
x86 said:
I know that upon release, it will do positive work on block B. But won't it also do positive work on block A?
Yes, assuming that both blocks are free to move, it will do work on both.

Based on your personal experience using springs to push things around do you think that a spring will push a block faster if the other side of the spring is pushing on a fixed wall or if the other side of the spring is pushing on another free block? (Assuming equal spring compression). What does that tell you about where the energy goes?

x86
DaleSpam said:
Yes, assuming that both blocks are free to move, it will do work on both.

Based on your personal experience using springs to push things around do you think that a spring will push a block faster if the other side of the spring is pushing on a fixed wall or if the other side of the spring is pushing on another free block? (Assuming equal spring compression). What does that tell you about where the energy goes?

If the spring is attached to a wall, then it can only decompress one way. Whereas if its between two blocks, it can do decompress both ways. So the block-wall spring should push the block faster.

I guess this means in the block-block spring, some of the energy is used to push both boxes. Actually, come to think of it, in both cases it transfers the same amount of energy. The only difference is the wall can't move., so its velocity is 0.

So then we still use the same formula for potential energy of the spring, 1/2kx^2. Right?

Right, the PE is the same, and just not all of it goes into block B upon release.

x86

1. How does a spring store potential energy?

A spring stores potential energy by being compressed or stretched. This causes the molecules in the spring to be pulled apart or pushed together, creating a force that can do work.

2. Does the potential energy of a spring do work on both ends?

Yes, the potential energy of a spring can do work on both ends. When a spring is compressed or stretched, the potential energy is stored in the spring and can be released to do work on both ends.

3. Can the potential energy of a spring be converted into other forms of energy?

Yes, the potential energy of a spring can be converted into other forms of energy, such as kinetic energy or thermal energy. This conversion occurs when the spring is released and the potential energy is transformed into motion or heat.

4. How is the potential energy of a spring calculated?

The potential energy of a spring can be calculated using the formula PE = 1/2 kx^2, where k is the spring constant and x is the displacement from the equilibrium position. The potential energy is measured in joules (J).

5. Does the potential energy of a spring change with the mass of the object attached to it?

No, the potential energy of a spring does not change with the mass of the object attached to it. The potential energy is determined by the spring constant and the displacement from the equilibrium position, not by the mass of the object.

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