Question

★ » Why Newton's Second law is called Real law ?

Explain .

Answer 1

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We shall now state that Newton's 1st law and the 3rd law is contained in 2nd law

According to Newton's second law :F=ma

If F=0 then a=0,m is unequal to 0

Which states that there will be no acceleration in the body if no external force is applied on it.This means that a body in rest will remain at rest and a body in uniform motion will remain in uniform motion which is also stated in Newton's 1st law.

Now,let F1 is the force exerted by a body A on B and F2 is the force exerted by body B on A .

Change in linear momentum of body A= F1×∆t

Change in linear momentum of body B=F2×∆t

Then,F1×∆t+F2×∆t=0

F1×∆t=-F2×∆t

F1=-F2

Action = Reaction,w hich is the third law of motion.

Therefore,2nd law of motion is a real law of motion.

Answer 2

》》Other laws of Newton can be derived from Newton's second law. Hence it is called real law of Newton.
FOR EXAMPLE:

2nd law is…F=ma

And 1st law is …initial velocity=final velocity

Assume that force acting on body is zero

F=ma

So, 0= ma

0/m = a

0=a

0= (v-u)/t

0/t = v-u

0= v-u

U=v

Thus ….we proved that 1st law can be derived from 2nd law of Newton.

Hope it is helpful....