Question

Define laws of newton's ?

Answer 1

$\huge\textbf{Newton's Law of Motion :}$
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$\textbf{1) Law of Inertia :}$

It is Newton's First law.

According to it an object at rest remains at rest, an object in uniform motion remains in uniform motion until or unless external force applied on them.

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$\textbf{2) Law of Force :}$

It is Newton's Second law.

According to it the rate of change of linear momentum is directly proportional to the external force applied.

F α dp/dt 

F = k dp/dt

Now,

p (momentum) = mv

So,

F = k d(mv)/dt

F = k md(v)/dt

F = k ma

(As, dv/dt = a)

Experimentally k =1

So,

$\textbf{F = ma}$

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$\textbf{3) Action - Reaction Law :}$

It is Newton's Third Law.

According to it, for every action there is equal and opposite reaction. [Equal in Magnitude but opposite in Direction.]

[DERIVATION is in Attachment !!]

$\textbf{F12 (vector) = - F21 (vector)}$

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Answer 2

Newtons first law of motion:

An object remains in a state of rest or of uniform motion in a straight line unless acted upon by an external unbalanced force.

Newtons second law of motion:

The rate of change if momentum of an object is proportional to the applied force in the direction of the force.

Newtons third law of motion :

To every action , there is an equal and opposite reaction and they act on two different bodies.