why certain quantities cannot have negative values?

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electronics_kumar

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why certain quantities( eg :speed) cannot have negative values?possessing only positive and zero
 

Can you attach a meaning to negative speed?
 

In your case, the speed menas the magnitude of the relocation vector. A magnitude, defined axiomly as a absolute value, cannot be any negative value. Such kind of things are confronted in physics a lot, where vectors or tensions are coming into play.
Most of the non-vectoral(i.e. scalar values) might be defined as negative values (e.g. electric charges).

Kind regards
 

Hello,
I am not sure but I think that we can imagine things which do not exist physically and talk about them.
It's like when we talk about asin(3) we know that sin is between -1 and 1 but in complex plane we can get inverse sines greater than 1.
Also I remember reading an essay on negative Energy (It's common to say that energy is only positive) but Dirac imagined the existence of negative energies and from that he got the idea of antiparticles which are proven to exist physically.
He said that if E=mc^2 then the antiparticle has Energy =-mc^2 and if we give him an energy =2 mc^2 he will show up as a particle not antiparticle...
I hope this helps,
Regards,
 

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