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At a much lower speed. When relativistic effects are negligible.

ohh but at low speed the effect is too small for us to even consider it ?

Responding here because of the nesting limit. If you want easy calculations, then you need to be non-relativistic. As soon as you go quick, relativity is at work and that's the price to pay. You can also achieve relativistic calculations at low speed and you will find that the results agree with the non-relativistic case.