Besides gravitational forces we come across many different types of forces such as the frictional force between two surface, the restoring force arising in compressed springs, tension produced in a stretched string, force of surface tension prevailing in the free surface of liquid, viscous force in fluid medium, intermolecular forces etc. Magnetic and electric forces are the origin of all these forces.
Four fundamental forces (interactions):
- The Gravitational force:
- The gravitational force is the force of mutual attraction between any two objects by virtue of their masses.
- It is a universal force.
- According to Newton's law of gravitation, this mutual attractive force is directly proportional to the product of their masses and inversely proportional to the square of the distance between them(inverse square law).
- It does not require any intervening medium.
- compare to other fundamental forces gravity is the weakest force of nature.
- In particular, gravity governs the motion of the moon and artificial satellites around the earth, motion of the planets around the sun and, of course, the motion of the bodies falling to the earth.
2. The Electromagnetic force:
- Electromagnetic force is the force between the charge particles.
- When charges are at rest, the force is given by coulomb's law; attractive for unlike charges and repulsive for like charges, the magnitude of the force obeying the inverse-square law.
- Charges in motion produce magnetic effects and a magnetic field gives arise to a force on a moving charge.
- Electric and magnetic effects are inseparable hence the name electromagnetic force.
- They are long range forces and hence they also don't need any intervening medium.
- The electromagnetic force between two stationary protons for example is 1036 times then the gravitational force between them, for any fixed distance.
- Gravitational force is always attractive in nature while electromagnetic force can be attractive or repulsive.
- Electromagnetic force also depends upon the medium prevailing between two objects.
3. Strong (nuclear) force:
- This force is responsible for binding protons and neutrons in a nucleus.
- It is evident that without some attractive force, a nucleus will be unstable due to the electric repulsion between the protons.
- The strong nuclear force is the strongest of all fundamental forces, about 100 times the electromagnetic force.
- It is charge, independent and acts equally.
- It is a short range force.
- Recent developments have indicated that this force is a Quark-Quark force.
- Neutrons and protons are being made of quarks.
4. Weak force:
- The weak force appears only in certain nuclear processes such as the β decay of a radioactive nucleus.
- In β decay, the nucleus emits an electron and an uncharged particle called neutrino.
- Thus weak force arises due to the interactions of neutrino with other particles.
- The range of weak force is exceedingly small, of the order of 10-15m.
- This force is responsible for the decay of free neutrons and mesons.
Recent developments indicate that the electromagnetic force and weak nuclear force are two aspects of a unified force known as "electroweak" force.
Fundamental force of
nature
nature
| Name | relative strength | Range | Operates among |
| Gravitational force | 10-38 | Infinite | All objects in the universe |
| Weak Force | 10-13 | Very short, within nuclear size | Elementary particles(neutrino) |
| Electromagnetic force | 10-2 | Infinite | Charged particles |
| Strong nuclear force | 1 | very short, within nuclear size | Nucleons (neutrons and protons) |
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