kuruman said:You are correct. The number is 2. Newton's 3rd Law says that forces come in pairs, so if you have a single force acting on an object (as in a free body diagram), you can safely deduce that there is another object (somewhere in the Universe and outside you free body diagram) that experiences a force of equal magnitude but in the opposite direction.
The four fundamental forces are gravity, electromagnetism, the strong nuclear force, and the weak nuclear force.
Gravity affects all forms of matter and causes objects to attract each other. Electromagnetism is responsible for the interactions between electrically charged particles. The strong nuclear force holds the nucleus of an atom together. The weak nuclear force is involved in processes such as radioactive decay.
These forces are considered fundamental because they are the basic interactions that govern the behavior of matter and energy in the universe. They cannot be broken down into simpler components and are necessary for understanding the physical world.
These forces work together to create the complex interactions and structures that we observe in the universe. For example, gravity holds galaxies together, while electromagnetism allows for the formation of chemical bonds between atoms.
Yes, there are theories such as string theory and the Standard Model of particle physics that attempt to unify these forces into a single, overarching theory. However, these theories are still being researched and are not yet fully understood or accepted by the scientific community.