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Newton's Laws of Motion I. Law of Inertia 11. F=ma III. Action-Reaction
Newton's laws of motion are of central importance in classical physics. A large number of principles and results may be derived from Newton's laws. Newton gave three laws governing the motion of bodies. We proceed with the statement of these three laws: First Law: According to this law, a body continues to be in its state of rest or of uniform motion along a straight line, unless it is acted upon by some unbalanced external force to change the state.
Explanation Of Newton's First Law: Newton's first law consists of three parts: (i) Without the application of an external force, a body at rest continues to be at rest. This part is self evident. For example, we find in day to day life that every object continues to lie where it is, unless we move it.
(ii) Without the application of an external force, a body in uniform motion continues to move uniformly. This part is slightly difficult to realise, because in everyday life, we find that a ball rolling on the ground does stop after sometime. Similarly, when the engine of a moving car is switched off, it stops after travelling some distance. Infact, motion of bodies is being opposed by the invisible forces like air resistance and force of friction between the body and the ground. If these force were removed, a body moving uniformly shall never stop on its own.
(ii)Without the application of an external force, a body cannot change its direction of motion i.e., It continues to move along the same straight line. For example, to turn a car moving over a straight road, we have to apply the force on the steering wheel of the car. Similarly, a bike cannot change its straight line path on its own. We have to turn its handle.
It should be clearly understood that the state of rest or uniform linear motion, both imply zero acceleration. Therefore, first law of motion can be expressed as: If the net external force on a body is zero, its acceleration is zero. Acceleration can be non-zero only if there is a net external force on the body. If an object on the earth is at rest or in uniform linear motion, it does not mean that no force are acting on it. Rather, it means that various external force acting on the body cancel out, i.e., these forces add up to zero net external force.
NEWTON'S FIRST LAW DEFINES FORCIE According to Newton's first law of motion, a body continues to be in state of rest or of uniform motion along a straight line, unless it is acted upon by an external force to change the state. This means force applied on a body alone, can change its state of rest or state of uniform motion along a straight line.
NEWTON'S FIRST LAW DEFINES INERTIA According to Newton's first law of motion, a body continues to be in a state of rest or of uniform motion along a straight line, unless it is acted upon by an external force to change its state. This means a body, on its own, cannot change its state of rest or state of uniform motion along a straight line.