Law of conservation of energy, i dont get it?

Question

energy cannot be created or destroyed, how do scientists now this? on what proof/basis is there. what formula etc

Answer 1

yes.. energy cannot be created or destroyed.. only be transfered....

Answer 2

"The energy cannot be created nor destroyed, but it can be transformed"

when we eat foods, the chemical energy on that food will be transformed into potential energy in our body. This potential energy will also be transformed into kinetic energy when we do something that requires force.

here's the logic:

food (chemical)- body (potential)- movement(kinetic)

meaning, the chemical energy in food was not destroyed but transformed into another form.

example 2:

in televisions:

electrical energy from socket ---- heat energy on tv

our television gets hotter the longer we use it, ryt?

there were also waste energy in every transformation (but very little in amount)...

Answer 3

let's suppose that water from ur over head tank overruns and pours out. that's a waste of electrical energy. Isn't it? but it's taken by the plants and living organisms right there. they suck them out to produce fruits (which is another form of energy[STARCH]). Which in turn s taken by us to get some energy  and this goes on............

And what u want to know is just this.

Answer 4

Scientists know this both empirically and theoretically.

Theoretically, the theory of motion that we use in basic physics is Newton's Theory of Motion. NTM, like all theories, begins with a small number of basic postulates. In this case, Newton's Second and Third Laws of Motion (The First Law you can leave out because it is derivable from the Second). The theory is the set of all logical consequences that are derivable from these postulates.

In this case, it is relatively easy to show that there is a certain class of force, called a conservative force, that conserves a certain quantity that we call energy. In order to derive this, you simply integrate both sides of the second law, F=ma, with respect to displacement. Your instructor should have done this in class for you if you are in a basic, calculus-based physics class. (If you are in an algebra-based physics class, don't expect very much to be proved to you). Since there are only two basic forces that operate in the classical world, gravity and electromagnetism, and both forces are conservative, then energy must always be conserved in the classical world.

Empirically, the law of conservation of energy makes very specific predictions about the outcomes of physical processes and experiments. People have been doing these experiments since 1745, and never have any of them violated the law. If they had, then we would have to throw out NTM as a good theory of motion.

Actually, in reality, we do, because NTM does not correctly predict the behaviours of subatomic particles. Of particular interest, the Casimir Effect, which is basically an experiment which does, in fact, violate conservation of energy at that subatomic level, because it shows that particles can arise spontaneously out of the vacuum. So we don't use NTM to talk about those very small systems: we use Quantum Mechanics (from which NTM can be derived mathematically for large macroscopic systems). In QM, energy must be conserved on average, but an amount of energy E can be created or destroyed, so long as the borrowed energy is returned within a time h/E.

I have bothered to write all this up because this is the way science "proves" everything. On the one hand, it is derived from basic principles, and on the other, its effects observed in the lab.

Answer 5

The equation is on wikipedia. Hopefully you can understand it better than I do.