How does potential energy actually turn into kinetic energy for a falling object? If I have two objects that aren’t in any way energized, motionless in space, how do they start moving? Each time I watch for this question it’s always “Gravitational force” which explains absolutely nothing. Energy can’t just start existing, so how does it work?

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Potential to kinetic Energy (...and back..)

Better example is pendulum. Bob has the largest potential energy at the maximum angle.

https://en.wikipedia.org/wiki/Pendulum

https://en.wikipedia.org/wiki/Pendulum_(mathematics)#Simple_gravity_pendulum

Edited January 5, 20188 yr by Sensei

Potential energy converting to kinetic energy is just the opposite of kinetic energy converting to potential.  Start with a rock at rest in your hand. Now throw it upwards. You are using energy stored in your muscles to impart kinetic energy to the rock. As it climbs, it slows giving up kinetic energy which is stored as potential energy. (just like when you stretch a spring it stores energy.)  Once it come to a stop, it falls back, reconverting the stored potential energy back into kinetic.

When you talk about two objects in space and separated from each other, you have to consider how they got there.  If you assume that they started together, then the potential energy they have was added by separating them.  If you just created them as being separated, you would not only have to supply the mass-equivalent energy to create the objects , but also the an amount of energy equal to the gravitational potential energy for their separation.  In either case, the potential energy didn't come from nowhere, but had to be supplied from somewhere.

Potential energy is a property related to the configuration of the system.

As such, it is not necessarily only about gravitational force.
While an arrangement of test masses will have gravitational potential, so will an arrangement of charges have electromagnetic potential.
Even two objects connected by a spring will have a potential energy due to their configuration.

The potential energy of an object is exchanged for kinetic energy once the potential forces that object into motion.
The motion of the object changes the configuration of the system, and increases/decreases the potential energy of the object.