* The force required to keep the part moving: This is called friction. Friction is a force that opposes motion and is caused by the interaction between surfaces in contact. The amount of friction depends on the materials of the surfaces and how tightly they are pressed together.

* The force that the moving part exerts on other objects: This is the force of impact if the part collides with something, or the force of tension if the part is pulling on something else. The magnitude of this force depends on the mass of the moving part, its velocity, and the nature of the interaction with the other object.

* The force that is causing the part to move: This could be any number of forces, such as:

* Gravity: If the part is falling, gravity is the force causing it to move.

* Applied force: If you are pushing or pulling the part, the force you are applying is what's causing it to move.

* Magnetic force: If the part is made of a magnetic material and is moving near a magnet, the magnetic force is what's causing it to move.

To give you a more specific answer, please provide more context:

* What kind of moving part are you talking about? (e.g., a car wheel, a gear in a machine, a ball rolling down a hill)

* What is the part doing? (e.g., rotating, translating, colliding)

* What is the context of the situation? (e.g., a car engine, a playground, a scientific experiment)