How we get motion 3rd law from 2nd law????
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Newton's 2nd law, F= ma.
Now,
let us consider a system of 2 bodies 1 & 2 and consider that there is no external force acting. Now, let F 12 be the force acting on 2 by 1 & F 21 be the force acting on 1 by 2.
The rate of change of momentum of 1 = dp1 /dt and rate of change of momentum of 2 = dp2 /dt
Thus, according to Newton's second law of motion F 12 = dp2 /dt and F 21 = dp1 /dt
Adding both the above equations, we get
F 12 + F 21 = dp2 /dt + dp1 /dt = d(p 2 +p 1 )/dt
We know that, no force is applied. Thus, momentum change will also be 0 because no change in velocity occurs.
Thus d(p 1 + p 2 )/dt = 0
Therefore, F 12 + F 21 = 0
That is, F 12 = - F 21.
Thus, Newton's third law is proved with Newton's second law.
Now,
let us consider a system of 2 bodies 1 & 2 and consider that there is no external force acting. Now, let F 12 be the force acting on 2 by 1 & F 21 be the force acting on 1 by 2.
The rate of change of momentum of 1 = dp1 /dt and rate of change of momentum of 2 = dp2 /dt
Thus, according to Newton's second law of motion F 12 = dp2 /dt and F 21 = dp1 /dt
Adding both the above equations, we get
F 12 + F 21 = dp2 /dt + dp1 /dt = d(p 2 +p 1 )/dt
We know that, no force is applied. Thus, momentum change will also be 0 because no change in velocity occurs.
Thus d(p 1 + p 2 )/dt = 0
Therefore, F 12 + F 21 = 0
That is, F 12 = - F 21.
Thus, Newton's third law is proved with Newton's second law.
RamagiriSaiganesh:
Sorry bro i want speed formulas ut+1/2at2
ohhh I'm sorry!! That's not law tho.. you should have said derivations of motion in 2d for constant acceleration
well I'm sorry I thought Newton's law cause you talked bout laws..
Answered by
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We can get it by deriving it
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Bro plzz explain last line clearly... Plzz.....
After multiplying 2 on both sides the ans will be the 3rd equation
Bro iam weak in maths. So plzz explain
After the step s=u×(v-u)/a + 1/2×(v-u)^2/a. Multiply 2as on both sides on both sides.Then answer will be 2as=2uv-2u^2+v^2-2uv+u^2 2as=v^2-u^2
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