Answer: When we use an analogy that represents the expanding universe with the surface of an expanding balloon, what does the inside of the balloon represent? The inside of the balloon does not represent any part of our universe.
Energy is the ability to do work.
So work can not be done without the transfer of energy from one body to another.
Work is the transfer of energy.
Hope this shows! It has all the equations for all of the problems u asked in the comments
law of conservation of energy
aka the first law of thermodynamics
