Force

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What is force?

Force is actually a push or pull which either changes or tends to change the state of rest or of uniform motion of a body.

It is very common which we all have observed that an object such as a chair lying in a room or vehicle part outside the house remains address unless push or pull is given to it. Such an object cannot move at its own. In other words, a force has to be applied in order to move an object at rest. Also, if a body is moving along a straight line with some velocity, it is found that force is required to change the direction of motion or the magnitude of the velocity. In other words, force is an agent, which causes acceleration.

However, in certain cases, the acceleration caused by the force maybe practically zero. For example, if you push to a stationary track, it may not move. In such cases force merely tends to cause acceleration.

Hence, we can define the force as a push or a pull that produces or tends to produce motion in a body at rest; stops or tends to stop a body that is in motion; increases or decreases the magnitude of velocity of the moving body or changes the direction of motion of the moving body.

Since a force causes the acceleration of a body, we now wish to define the unit of force carefully, in terms of acceleration that it gives two a standard reference body. As the standard body, we use (or rather we imagine that we use) the standard kilogram. This body has been assigned, exactly and why definition, mass of 1 kg.

We put the standard body on a horizontal frictionless table and pull the body to the right, so that by trial and error, it eventually experiences a measured acceleration of $ \displaystyle \text{1m/}{{\text{s}}^{2}}$. We then declare, as a matter of definition, that the force we are exerting on the standard body has a magnitude of 1 Newton (abbreviated N).

We can exert a 2N force on our standard body by pulling it so that it’s measured acceleration is $ \displaystyle 2\text{m/}{{\text{s}}^{2}}$, and so on. Thus, in general if our standard body of 1 kg mass has an acceleration ‘a‘, we know that force f must be acting on it and that the magnitude of the force (in Newton) is equal to the magnitude of the acceleration (in meters per second square)

Thus, a force is measured by the acceleration is produces. But acceleration is a vector quantity, with both magnitude and direction. Therefore, force is also a vector quantity; they have magnitude and direction and the combine according to the vector rules.

As like other vectors, of force or net force can have components along a co-ordinate axis. Finally, we note that Newton’s first law holds not only when there is no force on a body, but also when the net force is equals to zero.

The basic forces in nature

There are 4 basic forces that are operating nature:

1. The gravitational force

It is the force of attraction between the two object due to their masses. It has following properties:

It obeys Inverse Square Law.
It is always attractive in nature.
It is long range force that is it extends up to infinity.
The ‘graviton’ is the field particle of gravitational force.
It is the weakest force operating in nature.
It is central force and hence a conservative force.

It is because of the gravitational force of earth that all objects situated near the earth always fall towards its centre. Further, it is the gravitational force of earth that keeps moon and other satellite revolving around it.

2. The weak force

It is a force associated with beta decay in radioactivity. During the beta decay, a neutron inside the nucleus changes into a Proton electron and antineutrino (anti particle of neutrino). Neutrino is a neutral particle of approximately zero rest mass. In beta decay, the electron and the anti neutrino interact with each other through the week force. The leptons, interact with other leptons, mesons or baryons through weak force. The week force are about $ \displaystyle {{10}^{{25}}}$ times as strong as gravitational forces.

3. Electromagnetic force

The force between two stationery charges is called electrostatic force, while the force between two magnetic poles is called magnetic force. It is well known that a moving charge produces magnetic field and a charged particle moving in a magnetic field (not parallel to the direction of motion of charge particle) experience is a force. The electromagnetic force has fallen properties:

It obeys Inverse Square Law.
It may be attractive or repulsive in nature.
It is also a long range force.
The ‘photon’ is the field particle of electromagnetic force.
It is even stronger than weak force. It’s about $ \displaystyle {{10}^{{36}}}$ time is stronger than gravitational force and about $ \displaystyle {{10}^{{11}}}$ stronger than the weak force.
Is also a central and a conservative force.

4. The strong force

It is the force of nuclear origin. Because of this force, even protons attract each other inside the nucleus. In general, mesons and baryons interact with each other through strong forces. It has following properties:

It varies inversely with some higher power of distance.
It is basically and attractive force.
It is a short range force and is operative only over the size of the nucleus.
The pie mesons is IT field particles.
It is the strongest force operating in nature. It is about $ \displaystyle {{10}^{{38}}}$ times stronger than gravitational force and 100 times the stronger than electromagnetic force. The relative strength of the four types of forces are:
$ \displaystyle {{\text{F}}_{\text{G}}}\text{ : }{{\text{F}}_{\text{W}}}\text{ : }{{\text{F}}_{\text{E}}}\text{ : }{{\text{F}}_{\text{S}}}\text{ : : 1:1}{{\text{0}}^{{\text{25}}}}\text{ : 1}{{\text{0}}^{{\text{36}}}}\text{ : 1}{{\text{0}}^{{\text{38}}}}$
It is a non-central force.