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Newton's third law in noninertial frames 
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#1
Apr112, 11:56 AM

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Is newton's third law valid in noninertial frames? For example, in a rotating frame of reference, can Newton's third law still be applied? Or does the noninertial character of the frame violate it?



#2
Apr112, 02:57 PM

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#3
Apr112, 04:44 PM

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Hi Debdutta! Welcome to PF!
Yes, the forces will still be equal and opposite. 


#4
Apr112, 05:03 PM

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Newton's third law in noninertial frames
The forces acting between two objects do not depend on the coordinate system or referemce frame you use to measure them. So the third law always holds.
The second law is different: the apparent accelerations that you measure DO depend on the reference frame, hence the second law does not hold in a accelerating frame unless you add another term to the equation (a.k.a a fictitious force) to compensate for the acceleration of the frame. 


#5
Apr212, 01:57 AM

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So my next question is, can we assume that Newton's Third Law is still valid for interacting objects in any frame to test whether it is actually an inertial frame or not, that is, the first two laws of Newton hold or not?



#6
Apr212, 04:02 AM

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