Conservation of energy

Before, and that means after, and what's it? When is before and when is after? Pick any two times in the life of these particles.

It's like Law of Conservation of Energy, where we said E1 equals E2.

There, 1 and 2 stood for before and after.

Well, here we cannot use 1 and 2 for before and after, because 1 and 2 and 3 are labeling particles.

So, remember this elastic, inelastic collision.

This is in one dimension.

Now, I'll give you a typical problem where you have to be very careful in using the law of You cannot use the law of conservation of energy in an inelastic collision.

In fact, I ask you to check if two bodies, take two bodies identical with opposite velocities.

So even Earth's weather isn't a perpetual motion machine.

Now, there's a more fundamental reason why these machines are impossible, and it's called the law of conservation of energy, which states that energy can neither be created nor destroyed.

Energy never comes for free.

If you see a machine producing motion, heat, light, or another form of energy, keep looking for the energy source.

La photosynthèse.

C'est là où je m'amuse toujours quand les gens parlent en énergie, parce que pour moi, la photosynthèse, c'est un bel exemple de, où on viole la loi de conservation de l'énergie.

Pourquoi ? Ben j'ai pris le bilan tel qu'il est donné par un vrai scientifique qui s'appelle Ernst Zürcher, qui, lui, a étudié les arbres et qui nous donne des vrais chiffres.

Donc, deux choses déjà.

But it must be understood that it cannot of itself give us absolutely precise notions as to the nature of these phenomena, nor disclose their order of magnitude.

Section two, the principle of the conservation of energy.

Dominating not physics alone, but nearly every other science, the principle of the conservation of energy is justly considered as the grandest consequence of contemporary thought.

It shows us in a powerful light the most diverse questions.

It introduces order into the most varied studies.

And it supplies precise and exact numerical relations between the magnitudes which enter into these phenomena.

The boldest minds have an instinctive confidence in it, and it is the principle which has most stoutly resisted that assault which the daring of a few theorists has lately directed to the overthrow of the general principles of physics.

At every new discovery, the first thought of physicists is to find out how it accords with the principle of the conservation of energy.