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# Conservation of energy

Using the law of conservation of energy to see how potential energy is converted into kinetic energy. Created by Sal Khan.

## Want to join the conversation?

• Can anybody explain me what is dark energy?
• In physical cosmology and astronomy, dark energy is an unknown form of energy which is hypothesized to permeate all of space, tending to accelerate the expansion of the universe.

this is the real meaning
• energy can also be converted from one form to another , like wind energy is converted to electrical energy.but can sound energy be converted to light energy?
• This paper explores a relatively less popular source of clean energy. Noise (sound) energy can be converted into viable source of electric power by using a suitable transducer. This can be done by using a transducer by converting vibrations caused by noise into electrical energy. An application is proposed for the same, in which a speaker and a transformer are used to convert noise produced by car horn into electrical energy. The vibrations created by noise can be converted into electrical energy through the principle of electromagnetic induction. The received signal was stepped up using a transformer. A similar setup was placed at distance of 1 meter from the exhaust pipe of a 350 cubic centimeter engine of a motorbike. The demonstrated ideas probe into a clean and readily available source of energy.
• Why energy is conserved?
• good question simple and plain......

The total amount of energy in the universe is constant. To do something you use energy, but you don't really "use" it (as in it disappears), you just change it into something else (like motion or heat). Unless you don't mean how it's done, but actually "Why". Because that's like asking what the meaning of life is... I can give you a lot of answers but none of them are really right. But I guess this is where that principle that "If such and such hadn't been like that, we wouldn't exist." If energy was just lost gained randomly.. you could go "poof" any second.
• unit and others like this need to be updated as it becomes difficult to read the writing. The writing seems very pixilated and harder to read.
• According to the law of conservation of energy, is the amount of energy on Earth a fixed amount, because energy cannot be created or destroyed?
• The earth is not a closed system so the amount of energy is not constant.

The earth is gaining energy from the sun and losing energy to heat loss to space.
• So essentially i did exactly what sal did at however i used both methods: the kinematic way and the energy way. For the kinematic way i get v^2=196 and for energy way as sal stated we get v^2= 200 now i realise the difference is not huge with V=14ms/s for the kinematic way and V=14.14m/s for the energy way, but why does the difference exist if both methods can determine the same results?
• Because in the kinematic you used 9.81m/s^2 for the gravity. You forgot that in this video the acceleration for the gravity in this video is 10/s^2 for the sake of simplicity.
• If energy is neither created nor destroyed, then how do we get energy?
• Energy is neither created no destroyed in the universe as it exists.
That rule would not necessarily apply to the creation of the universe itself.
But all the energy that's in the universe now is what was there when the universe started. How it got there, we don't know, just like we don't know how the universe started
• The law states that the Potential Energy at the top of the object equal of that to the Kenetic Energy of the Object before it hits the ground. At that point height is not entirely zero, Does this mean that PE top is not equal but approximate to KE bottom?
• no, it means you are measuring PE incorrectly. What the law says is that the change in the KE will be equal to the change in the PE. You can set zero PE wherever you want.