In our daily life, we come across many type of forces, for example, muscular force, frictional force, elastic force, magnetic force, etc., All these forces are included in four basic types of forces operating in nature. These are gravitational forces, weak forces, electromagnetic forces and strong forces.

### a) Gravitational Forces

The forces of attraction existing between any two separated bodies due to their masses are called 'gravitational force'. These forces have following properties:

1) Gravitational Force between two bodies are always attractive.
2) They obey inverse-square law, that is, they very inversely as the square of the distance between the two bodies.
3) They are 'central forces' that is, they act along the line joining the centres of the two bodies. Hence they are ' conservative ' forces.

### b) Weak Forces

The weak forces were discovered during the study of beta emissions from nuclei. During beta emissions, a neutron inside the nucleus is converted into proton, an electron and an antineutrino, a particle having no charge and almost zero rest - mass.
Thus, weak forces are the forces which cause light elementary particles to interact with one another and with heavier particles.
These are about 10^26 times stronger than the gravitational forces. The field particles of weak forces is ' neutrino '.

### c) Electromagnetic Forces

These forces include electrostatic force and magnetic force. The force between two stationary charges is 'electrostatic force' while the force between two magnetic poles is 'magnetic force'. These forces are not independent phenomena. A moving company charge produce a magnetic field, while a charged particles moving in a magnetic field experiences a force. Thus, electric force and magnetic force are two aspects of electromagnetic forces. The electromagnetic forces have following properties:

1) They may be attractive and repulsive. Like charges and like poles repel each other, while unlike charges and unlike poles attract each other.
2) They obey inverse-square law.
3) They are central forces and hence they are conservative.

### d) Strong Forces

These forces are of nuclear origin. They are responsible for holding neutrons and protons  together inside atomic nucleus. They have following properties:

1) The nuclear forces are basically attractive forces. They exist between neutron and neutron, between proton and proton and between neutron and proton inside the nucleus.
2) They do not obey inverse-square law.
3) They are ' non-profit central ' and hence ' non-conservative.