Physics Energy Watch
I get that it is the energy possessed by an object due to its motion or position. It can either be kinetic or potential.
Yet, is it not the same as internal energy because they are both the sum of kinetic + potential + why call something mechanical when it is basically the same as kinetic anyway practically. I'm confused.
Can someone explain simple terms what it is? Thanks
A single atom has a potential relative to other atoms, and a kinetic energy with its motion. In a gas, we don't just say "X atom has this potential and energy, and Y has this" but we refer to the actual gas itself as having this internal energy associated with it.
Equally, a single planet has an energy associated with its rotation about the sun, and a potential energy associated with that. The total energy of the solar system may be considered to be the sum of these internal energies of all the constituent particles.
In both cases, the system can actually be moving. The gas may be in a container being ferried off somewhere. It has some internal energy owing to the interactions between the particles within the gas, and it then has an energy associated with the container of the gas itself. The solar system has the internal energy owing to the planets, but the system itself moves around the galactic centre, and may be considered to have a kinetic energy associated with that if you consider the entire system that the galaxy is.
From how I understand it, it depends on the "multi-particle system" in question. Think of your system. If you're talking about a bulk of lots of particles and describing the bulk motion of this system, you're dealing with the "mechanical energy" of the system. If you're talking about the energy actually in the system, like the heat in the air that moves around the air, you're talking about the interactions between the particles in the system themselves, which should count as the internal energy.
That's my understanding, anyway. Hope that helps! I tried to keep it reasonable.