eli5: Where does energy spent go?


The law of conservation of energy states that energy cant be created nor destroyed, but, when lets say i punch a wall or run i spent some energy, where does that energy go?

In: Physics

Punching a wall, which was fueled itself by consumption of food, transfers to kinetic energy when the wall is struck.

Usually it turns into heat. Heat is the most useless form of energy – it’s what we call energy that’s spread itself out as much as it can.

The ELI5 answer is sound and heat, unless you broke the wall when punching it, then some of it went into “plastic deformation” or the permanent movement of some material relative to others. The noise is from the sheetrock deflecting or breaking, and that pushing air molecules and starting the vibrations which become sound.

Also, things that move, like the sheetrock and studs behind it, keep vibrating until they are damped out by dissipative forces like friction, and that ends up as heat.

Every form of energy transforms and eventually decays into small amounts of heat, when you punch a wall some energy gets dispersed into sound waves, while most of the rest “moves” atoms inside the wall producing heat.

For example you could coock a chicken if you slapped it arround 23 000 times, or you could coock it in one single, inhuman, slap: [https://www.futurescienceleaders.com/yvr1b/2019/02/25/how-many-slaps-does-it-take-to-cook-a-chicken/](https://www.futurescienceleaders.com/yvr1b/2019/02/25/how-many-slaps-does-it-take-to-cook-a-chicken/)