The kinematics equations are the equations which are used to describe the motion of a kinematics particle completely i.e. using this we can easily solve for the each step of the motion of the particle. There are two such equations which are given below:
Basic Equations Related to Kinematics
Position Time Equation:

Consider an object moving with a uniform acceleration along a straight line OX with the origin at O. Let the object reach at points A and B at instants t1 and t2. Let x1 and x2 be the displacements of the object at times t1 and t2 respectively and v1 and v2 be the velocities of the object at positions A and B respectively as shown in figure below.

Figure showing Object displacement at different times

The acceleration of the object is given by

a = change in velocity / time taken

Thus a = v2 - v1 / t2 - t1

or v2 - v1 = a (t2 - t1)

or v2 = v1 + a (t2 - t1) !!! (1)

Let the origin of the time axis be taken at A and u is the velocity of the object at A. v is the velocity of the object at B after time t. Then

v1 = u; v2 = v; t1 = 0; t2 = t.

Thus we get

v = u + at !!! (2)
Position Velocity Equation:

For the object discussed above the average velocity is

vav = (x2 - x1) / (t2 - t1)

and (x2 - x1) = vav (t2 - t1)

But generally vav is given as

vav = (v1 + v2) / 2

Thus (x2 - x1) = (v1 + v2) / 2. (t2 - t1)

From equation (1) we have

(t2 - t1) = (v2 - v1) / a

Now using this we get

(x2 - x1) = (v1 + v2) / 2. (v2 - v1) / a

(x2 - x1) = (v22 - v12) / 2a

or v22 - v12 = 2a (x2 - x1)

As v2 = v; v1 = u; take x1 = x0; x2 = x

Thus v2 - u2 = 2a (x - x0)

If x - x0 = S

Then v2 - u2 = 2aS.
Conclusion for the Basic Equations in Kinematics

As per the kinematic equations so obtained, we refer these equations in describing the motion of a body. These equations related to position, velocity and time are helpful in solving analytical problems in different branches related to science.

The basic forces in nature can be classified into four categories depending upon their nature and relative strength. They are

1. Gravitational force 2. Electromagnetic force 3. Strong Nuclear force 4. Weak Nuclear force.

Any phenomenon that occurs in nature can be understood in terms of any of the basic forces or a combination of forces between the bodies.

Gravitational force:

Gravitational force is responsible for the attraction between particles of various bodies having some mass. Gravitational force is the weakest of all the four basic forces. It is in fact weaker than the 'weak nuclear force'. It is a long range force i.e., it pervades the whole universe, wherever the bodies with some mass exist. Though gravitational force is the weakest, it becomes appreciable when at least one of the interacting bodies is massive like the sun and earth or the earth and a stone. This weakest force, in fact, causes objects to fall, determines the motion of celestial bodies and gives rise to ocean tides. Many such natural phenomena can be explained in terms of gravitational force. Gravitational force is always an attractive force and i believed to be communicated through a particle called graviton.

Electromagnetic Force

The electromagnetic force is dominant on the atomic level and is responsible for holding the atoms together that make up the molecules. It also binds the electrons of an atom to the nucleus. Apart from determining the properties of atoms and molecules electromagnetic forces are also responsible for other kinds of forces such as friction, air resistance, elasticity, tension etc. It is a long range force and extends up to infinity. This force is either attractive or repulsive depending upon the type of charge of the interacting particles. Electromagnetic force is communicated through particles called photons.
Basic Forces in Nature (cont)

Strong Nuclear Force

Strong nuclear force is responsible for holding the protons and neutrons in the nucleus. The force acting between the nucleons is called the strong nuclear force. This force may act between any pair of nucleons-proton-proton; neutron-neutron and proton-proton.

The strong nuclear force is a short range force, i.e., it falls off very quickly with the distance between the interacting particles. Nuclear force does not extend outside the nucleus. Nuclear force is basically attractive in nature. However when the distance between two nucleons is of the order of 0.4 fm it becomes repulsive. It is communicated through `pi` - mesons.

Weak Nuclear Force:

Weak nuclear force is responsible for a type of radioactive decay known as beta decay and other similar decay processes involving fundamental particles. It acts between all leptons(electrons, positrons, `mu` - mesons and neutrinos) and hadrons (mesons and baryons). It is also a short range force. It is communicated through weak bosons.
Relative Strengths of Basic Forces in Nature

Basic Force
Relative Strength Range
Gravitational 1 Long Range, Infinite
Weak Nuclear 1031 Extremely short range <<e fm
Electromagnetic 1036 Long Range, Infinite
Strong force 1038 Short Range, 1 fm

The most recent advances in particle physics suggest that the electromagnetic force, the weak nuclear force and possibly strong nuclear force may all be the same type of interaction or a unified force. Scientists Are trying to formulate ' Theory of Everything' in which all the four known forces will be integrated or unified.