F3 Physic Question

I suppose you refer to the kinetic energy of molecules in a substance.

Because of thermal agitation, not all molecules in a substance have the same kinetic energy. Some have higher energy and some have lower energy. The total kinetic energy of these molecules is just the sum of the kinetic energies of individual molecules.

For example, if there are N molecules, having kinetic energies of E1, E2, E3 ...En for thess N molecules.
The total kinetic energy = (E1 + E2 + E3 + .... + En)

The average kinetic energy = (E1 + E2 + E3 + .... + En)/N

Thus, average kinetic energy is a representation of the molecular kinetic energy of a substance as a whole.

Similar argument applies to molecular potential energy.

The total kinetic energy refers to the sum of kinetic energy of all the molecules in an object.So the amount of molecules can affect the total kinetic energy of an object.

But the average kinetic energy is the mean of the kinetic energy an object has.So only the types of the molecules can affect the average kinetic energy of an object.


For example,a glass of water has more total kinetic energy than a drop of water at the same temperature.But they have the same amount of average kinetic energy because both of them are water.

Potential energy is based on the same theory.