The discussion revolves around the frame independence of Newton's third law, exploring the relationship between real forces and their independence from reference frames. Participants examine definitions, implications of Newton's second law, and the distinction between inertial and non-inertial frames.
Participants express differing views on the frame dependence of Newton's third law, with some asserting it is frame independent while others argue it is dependent on the context of inertial versus non-inertial frames. No consensus is reached on the implications of fictitious forces.
Participants highlight the need for clarity regarding definitions and the assumptions underlying the discussion, particularly concerning the nature of forces in different frames of reference.
Per definition.parshyaa said:so tell me how real forces are frame independent?
Ok I agree, but can you give me a reason or explanation which made scientist or anyone to frame it as a definition. how can you say that this definition is correct.A.T. said:Per definition.
Definitions are neither correct nor false.parshyaa said:how can you say that this definition is correct.
This can be proved from the Newton second lawparshyaa said:how can you say(prove) that Newton's third law is frame independent. you will say that as real forces are frame independent , therefore Newton's third law is also frame independent, so tell me how real forces are frame independent?
parshyaa said:so tell me how real forces are frame independent?
Real forces are frame independent even across non-inertial frames, so I assumed this is what the OP asks about. As for the main question, Newtons 3rd Law holds only in inertial frames.Demystifier said:The transformation from one inertial frame to another
Yes you are right that Newtons third law is frame dependent, because fictitious force can't be felt, its a imaginary force, then how it can have a reaction pair , thanks.A.T. said:Real forces are frame independent even across non-inertial frames, so I assumed this is what the OP asks about. As for the main question, Newtons 3rd Law holds only in inertial frames.
Yoo right , we can also prove it without using galilean transformation,let S and S' be inertial frame of reference, let 'P' be a particle in S', therefore aPS' = aPS - aS'S, since S' is moving uniform to S , aS'S = 0 , therefore aPS' = aPS , as accelaration of particle is same in both frames and mass is same(here) , force will also be same.Demystifier said:This can be proved from the Newton second law
$$F=m\frac{d^2x}{dt^2}.$$
The transformation from one inertial frame to another is given by the Galilean transformation
$$x'=x+vt ,$$
where ##v## is a constant velocity of the frame relative to the other frame. Since this transformation is linear in ##t##, we have
$$\frac{d^2x'}{dt^2}=\frac{d^2x}{dt^2} .$$
Therefore, ##d^2x/dt^2## is frame independent. Assuming that mass ##m## is also frame independent, from the Newton second law above it follows that the force ##F## is frame independent. Q.E.D.
For the same reason time moves from past to future.parshyaa said:...my question was only why gravitational force is attractive?
Before asking how a fictitious force can have third-law partner, you must ask whether it has a third-law partner.parshyaa said:Yes you are right that Newtons third law is frame dependent, because fictitious force can't be felt, its a imaginary force, then how it can have a reaction pair , thanks.