Conservation of energy | Physics | Khan Academy

Energy is a conserved quantity. If a system is isolated, the total energy of the system remains constant as energy converts from one form to another. If a system is not isolated, the total energy of the system can change. However, the amount by which the system's energy changes is exactly equal to the amount of energy that transferred to or from the surroundings.

Sections:
00:00 - Intro
00:16 - What is a system?
01:35 - Applying conservation of energy
04:26 - Energy conservation with friction
08:00 - Energy conservation in orbits
09:50 - Energy conservation in approaching nuclei
13:50 - Energy conservation in electron transitions

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[confidosine]

For the first example, you also have to assume that the normal force exerted by the ramp is always perpendicular to the ball's velocity so that the work done by it is 0. And if it is rotating it becomes more complicated because some of the potential energy is also converted into rotational kinetic energy.

[sardarbekomurbekov]

Is it coloumb's law in equation for calculating distance r? Should r be squared?