AQA A-Level Physics/Particles and Anti-particles/Forces
You may have learnt that there are many different types of forces such as friction and tension. However only four fundamental forces are at a basic level responsible for all interactions in the universe.
Strong Nuclear ForceEdit
This type of force is only experienced by hadrons (baryons and mesons). The exchange particles for this force are gluons. This force is responsible for keeping the protons and neutrons in a atomic nucleus together. The strong nuclear force only acts over a short range of 3fm. Between the distance of 3fm and 0.5fm separation the strong nuclear force is attractive. Below 0.5fm separation the strong nuclear force is repulsive.
Weak Nuclear ForceEdit
This type of force is experienced by both hadrons and leptons. The exchange particle for this type of force is the W or the K boson. This force is responsible for decay interactions (such as beta decay) and interactions where strangeness is not conserved or where quarks change flavour (or type).
This type of force is experienced by particles which are charged (such as electrons and protons). The exchange particle for this type of force is the virtual photon. This force is responsible for the repulsion of two electrons and attraction of an electron to a proton.
This type of force is experienced by all particles in the universe which have mass. The exchange particle for this force is not known and you will never be asked to mention it, but if you're curious, it is theorised that this force functions slightly differently to the other three. This force binds together all mass in the universe. No matter how far you stray from something, you will always be attracted to it, although the strength of this weakens with separation.