Naked Science Forum

Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: jeffreyH on 31/12/2014 21:11:57

Title: Acceleration and magnetism
Post by: jeffreyH on 31/12/2014 21:11:57
If two bar magnets were held together south pole to south pole or visa versa in the absence of any other fields and then released would they start moving away by accelerating and then reach an equilibrium velocity or continue accelerating to infinity.
Title: Re: Acceleration and magnetism
Post by: alancalverd on 31/12/2014 23:57:51
F = Ma

If F > 0 then a > 0

F = B1B2/r2 > 0 for all r
Title: Re: Acceleration and magnetism
Post by: jeffreyH on 01/01/2015 00:33:38
Quote from: alancalverd on 31/12/2014 23:57:51
F = Ma

If F > 0 then a > 0

F = B1B2/r2 > 0 for all r

Thanks
Title: Re: Acceleration and magnetism
Post by: evan_au on 01/01/2015 10:41:40
If the magnets were in space, but fixed in alignment via a hypothetical taut string of infinite length and zero friction, then they would continue accelerating forever. With an acceleration force which declines with the square of distance, if they start off with a non-zero initial separation (determined by the physical size of the magnets), then I expect they will asymptotically approach a finite separation velocity.

However, in practice, if the magnets were in space with no alignment mechanism and released, they would flip around so they are facing North to South poles, and clamp together, reaching zero acceleration and zero velocity immediately.
Title: Re: Acceleration and magnetism
Post by: jeffreyH on 01/01/2015 16:43:18
Quote from: evan_au on 01/01/2015 10:41:40
If the magnets were in space, but fixed in alignment via a hypothetical taut string of infinite length and zero friction, then they would continue accelerating forever. With an acceleration force which declines with the square of distance, if they start off with a non-zero initial separation (determined by the physical size of the magnets), then I expect they will asymptotically approach a finite separation velocity.

However, in practice, if the magnets were in space with no alignment mechanism and released, they would flip around so they are facing North to South poles, and clamp together, reaching zero acceleration and zero velocity immediately.

That's an interesting conclusion.