## Saturday, 20 July 2013

### Fundamental forces of Nature

 This chapter deals with the concept of gravity, electromagnetic force and nuclear force. You can skip this section if you wish to.

In our surrounding, there are several forces acting, such as frictional force, electrical force, muscular force when scrolling down the page, tension etc. But this forces form a part of Macroscopic forces, which are discussed under classical physics. At microscopic level, there are 4 recognized forces of nature which form the base for all other forces. These forces are discussed below.

Gravitational force : It is described as the most basic force that arises due to mass. It is a attractive force. According to Newton, gravity or gravitational force is the force due to mass of a body which is why every matter in this universe is attracted to every other matter. However Newton could not explain the cause of this force. Einstein's General Relativity explains the cause of this force that would be discussed later. Classical physics states that it is the force of gravity that makes orbits of celestial bodies, new stars,galaxies etc.

Electromagnetic force : Electromagnetic force is the force between the charged particles. For more information on particles refer Particle Physics. When charges are at rest, like charges repel each other and unlike charges attract each other. Charges in motion generate electrical and magnetic field that causes the electrical and magnetic effects called electromagnetic effects. Electromagnetic force can occur over large distances. In fact electromagnetic force is 1036 times powerful than gravitational force. Thus in an open space, two protons (positively charged particles) are likely to repel each other due to electromagnetic force than attract due to Gravity. Similarly you are easily able to lift a book because the electromagnetic force offered by your hand is much more than the gravitational pull of the earth. In fact if the electromagnetic force won't have been so strong, we would have crumbled under our own weight.

Strong Nuclear force : The strong nuclear force binds the protons and neutrons in a nucleus. It is evident that without some attractive force, atomic nucleus won't have exist as protons would have repelled. It is strongest fundamental force of all. It is about 100 times stronger than electromagnetic force. The force of gravity is negligible in comparison to strong nuclear force. It must be notes that electrons doesn't  experience such force. It is this force responsible for atomic stability. The range of strong nuclear force is, however, very small ranging from 10-15 to 10-14m.

Weak Nuclear force : The weak nuclear force appears only in certain nucleus such as beta-decay (Refer Radiations to know more about beta particles). The weak nuclear force is weaker than electromagnetic and strong nuclear force. The range of weak nuclear force is exceedingly small, of the order of 10-16m.

It is these fundamental forces of nature that cause all other forces. A resultant force is the vector or algebraic sum of all the force acting on a body or particle at macroscopic and microscopic levels respectively.

The following video would help you understand the four fundamental forces :

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