Zhengi Wu posted an interesting question in the comments, I wanted to include a diagram in my answer so thought I would write a blog post about it, here is the question:

Hi Chris，

I saw this worked example in a textbook:

Q: You stand on roller skates facing a wall. You push against the wall and you move away. Discuss whether the force exerted by the wall on you performed any work.

A: No work was done because there is no displacement. You moved but the point where the force is applied never moved.

I would think there's some problem with this answer. Where does my kinetic energy ("move away") come from if no work is done?

And my answer:

That's an interesting one. The wall can not do any work as it has no energy. The person is the one doing the work, they are using the energy from the food they have eaten. The force is exerted by the arms but the arms are connected to your body, let's simplify this by considering a massless spring between the wall and the skater, the spring pushes the wall and the skater, the wall doesn't move but the skater does, the spring does work on the skater, the force is in the direction of movement but it isn't the force of the wall on the spring, it is the spring on the skater. The confusion comes from the fact that the spring (arms) is connected to the skater so moves with the skater.

I set this up in Algodoo:

Here it is clear that the normal force between hand and wall is not the force pushing the skater. Note that the normal forces between spring and skater and spring and wall are not the same, the forces on the spring are not balanced, the right end of the spring will move but not the left. I have omitted the force of the spring on the end blocks, the following diagram only has the spring force.

Now you can see why the end right end moves but not the left.