How are other forces related to Gravitational, electromagnetic, and nuclear forces?

Answer 1

All forces can be traced back to one or a combination of the four fundamental forces: strong and weak atomic that hold atomic nuclei together, electro-magnetic, and gravitational.

For example, waterfalls create force to convert kinetic energy into electrical energy. The molecules making up the water are made of atoms held together by the atomic forces and surrounded by EM force (the electrons). Gravity movtivates the molecules to give them kinetic energy. When they strike the blades of the generator, they are prevented from penetrating the blades by EM forces surrounding the atoms that make up the blades. Consequently the water changes direction and that causes the blades to move because a change in direction pushes them.

There are probably other instances of the four forces at work in a waterfall, but you get the idea. All forces in the universe can be broken down into their elemental parts and when that's done, we find there are only the four fundamental forces.

Answer 2

They are the only FUNDAMENTAL forces we know of. Others eventually come down to these four. For example, van der Waals forces are electrostatic. If you pull on a rope, you are stretching chemical bonds, which are also electrostatic.

Answer 3

they are the third cousins