Here in this chapter, we would take our understanding one step further to learn abouts origins of acceleration or force
Here we will specifically consider the cause behind the moving objects i.e what causes the objects to move
Thus we will learn the theory of motion based on the ideas of mass and force and the laws connecting these physical concepts to the kinematics
quantities
So we will begin by stating the Newton's law's of motion which are of critical importance in classical mechanics
Laws of motion as stated by Newtons in his principle are
(i) Every body continues in its state of rest or uniform motion in straight line ,unless compelled to change that state by force imposed upon it
(ii) Change of motion of an objects is proportional to the force acting on it and is made in the direction of the straight line along the direction of force
(iii) To every action there is always an equal and opposite reaction
(2) Force
Concept of force is central to all of physics whether it is classical physics,nuclear physics,quantum physics or any other form of physics
So what is force? when we push or pull anybody we are said to exert force on the body
Push or pull applied on a body does not exactly define the force in general.We can define force as an influence causing a body at rest or moving with
constant velocity to undergo an accleration
There are many ways in which one body can exert force on another body
Few examples are given below
(a)Stretched springs exerts force on the bodies attached to its ends
(b)Compressed air in a container exerts force on the walls of the container
(c) Force can be used to deform a flexible object
There are lots of examples you could find looking around yourself
Force of gravitational attraction exerted by earth is a kind of force that acts on every physical body on the earth and is called the weight of the
body
Mechanical and gravitation forces are not the only forces present infact all the forces in Universe are based on four fundamental forces
(i) Strong and weak forces: These are forces at very short distance (10-05 m) and are responsible for interaction between neutrons and proton in
atomic nucleus
(ii) Electromagnetic forces: EM force acts between electric charges
(iii) Gravitational force -it acts between the masses
In mechanics we will only study about the mechanical and gravitational forces
Force is a vector quatity and it needs both the magnitude as well as direction for its complete description
SI unit of force is Newton (N) and CGS unit is dyne where
1 dyne= 1005 N
