# Recent content by Enryque

1. ### How to Determine the Axis of Rotation

We can assume a flat motion system. Then we have 3 independent variables in the context of an inertial coordinate system : (x,y) for the position of the center of masses and φ for the bar's angle. From this information you can calculate the potential energy due to gravity an due to the strings...
2. ### I A problem about momentum conservation.

As I belive, the fields of the two puntual charges are, in modulus,like this (R.K. Wangsness - Electromagnetic Fields) Erest=q/4πεr ; Emotion=Erestf(v,θ) if we put the two charges aligned with the relative velocity θ=0 and we have Emotion=Erest(1-v2/c2) so the force on the charge at rest...
3. ### I A problem about momentum conservation.

Thanks for your soon response and adjust the level. It seems I agree with you about the locality and causality; however the problem is no clear for me. I suppose that this problem can be addressed clasically, with the idea that the force on a charge equals the product of the charge value by...
4. ### I A problem about momentum conservation.

Imagine two equal charges, one at rest and the other moving uniformly. From Special Relativity we know that the electric field of the moving charge is different respect the one of the charge at rest. So the two forces of the interaction do not verify the law of action-reaction and there is a...