Whilst the oven is on cooking what I fancy for my dinner I’ve always filled any empty shelves with food that could do with being baked and then frozen it for another day with the belief that I am saving energy by using up what would otherwise be wasted space in a hot oven, however, my question is this: am I in fact wasting energy by placing items upon an empty shelf that will now absorb energy to cook, energy that the oven must work to replace? Would it have been more efficient to leave the shelf empty so the oven needs only maintain the temperature?

Whilst studying Mechanics (M1), you often use "light and inextensible" to describe string. So my friend posed a hypothetical question that if you had some string that was 1million light years long with me on one end and him on the other. If he pulled one end how long would it take for the my end to move. I thought it would be instantaneous but my teacher thought different.

Human beings have identified four fundamental forces of nature (the strong nuclear force, the weak nuclear force, the electromagnetic force, and gravity), and it appears that these four fundamental forces enable us to account for everything we observe in the universe (including all matter – i.e. all particles and subatomic particles are understood to be stable manifestations of these four fundamental forces). It appears that all other forces observed in nature can be derived from these four fundamental forces.

If it is correct that Energy is defined not by what it is but by what it can do, then is it correct to assume that energy must be some measure of the fundamental forces of nature acting upon one another?

The fact that mass (such as matter) can be converted into energy (such as in a nuclear explosion) in accordance with Einstein’s equation suggests that everything we observe in the universe is simply the various stable manifestations of the four fundamental forces acting upon one another. If this is correct, then what is a force, exactly (i.e. what is a force, not what does it do)?

According to the second law of thermodynamics, the energy of a closed system always tends towards equilibrium (because an equilibrium state has a higher probability than any other) and the overall entropy always increases. Can energy (all forms including heat, potential energy, kinetic energy, chemical energy etc.) be explained and defined by the fundamental forces of nature tending towards equilibrium?

My girlfriend and I were having an argument the other day. Sometimes when it is cold in the kitchen, I turn in the gas hob to warm the place up. The argument is that she claims that the room gets hotter if you put a pot of water on the hob to boil and let the room get steamy. I disagree and think that the room gets just as hot without boiling a pot of water.

Who is right? Does the room get hotter with the pot of water or does the room get just as hot without it?