What happens to the spring when a force is applied to a block compressing it against a wall?

When a force is applied to a block that compresses a spring against a wall, the spring responds by exerting a force back in accordance with Hooke's Law, which states that the force exerted by a spring is directly proportional to its displacement from its equilibrium position. This means that when the spring is compressed, it generates an equal and opposite force that tries to return to its original, uncompressed state.

This reaction is a crucial aspect of how springs operate; they resist deformation and attempt to restore their shape when a compressive force is released. Thus, even though the spring is being compressed by the block against the wall, it will exert a force back against the block and the wall.

While the other answers may contain elements of truth in different scenarios, they do not accurately focus on the primary behavior of the spring in response to applied forces. For instance, while the spring remains compressed, this does not capture the essential dynamic of the spring's force output. Similarly, stating that the block moves only overlooks the mechanical interaction between the block and the spring. The key point here is that the spring exerts a counteracting force whenever it is deformed, which is why the choice emphasizing the spring's force is the most correct.