Question

state newtons 2 law .explain how it gives definition of force .explain how it contain 1 law

Answer 1

the rate of change in momentum is directly proportional to the force applied and this change acts in direction in which force acts.

Answer 2

Newton's 2 law :- Rate of Change of momentum is directly proportional to Force applied.

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Given rate of change of momentum is directly proportional to its Force applied. 

First of all

Momentum =P = mv 

Rate of change of velocity = Pf - Pi /t

Here Pi is the initial momentum, 

Pf is the final momentum 

now

Pf - Pi /t ∝F 

mv- mu /t ∝ F 

we know that final and initial velocities are considered v,u respectively. 

m( v - u)/t ∝F 

F ∝ ma 

here we take acceleration = v-u/t

So for removing proportionality I am introducing a proportionality constant Say K 

finally F= maK 

here K =1 

Finally F = m* a 

Thus, after deriving, it gives definition of force.
Force is the product of the mass of the object and acceleration produced. 

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And as we saw here, Only force can change the state of rest or motion. A object which is in rest have no change in momentum, because it has no force applied. this is how 2 nd law defines first law.

Newton's First Law of motion :- A body continues to be in rest or uniform motion until unless an external force acts upon it.