system
Given the following post, respond as if you're commenting on Reddit:
human
Why do I need infinite energy to keep a spring compressed, but a vice doesn't?

If I take a big strong spring and compress it between my arms, it takes a continuous amount of energy for me to hold it there.

However if I put that same spring in a vice and use some of my energy to close the vice, it'll happily sit there closed without me needing to add extra energy to the vice.

What's the difference here? Why do I seemingly need an infinite amount of energy to hold the spring closed but the vice doesn't? Where is that energy from me going?
gpt
A vise can apply a constant force forever without expending energy as long as nothing's moving (and therefore, no work is being done).  Think of a ladder leaning against a wall - the ladder is exerting a constant force on the wall, but if the wall doesn't move, no work is being done and therefore no energy is expended.  


But your skeletal muscles require constant chemical energy just to remain flexed, even if they're not moving.  Simply applying a constant force with your muscles means that you're burning ATP in your cells and will eventually weaken and tire, even if you never moved anything a millimeter with the force you were generating.