Relativistic Effects: When to Consider v/c Ratios

[Sonko]

at what sort of speed ratio (v/c) would one consider relativistic effects to become important? i would probably say when v/c ~ 0.4 as this would make the gamma factor to be ~ 1.1, making a 10% difference (for length contraction, time dilation etc..). is there any "offical" value for where one should begin to consider the effects?

thanks

 

[mgb_phys]

Depends on how accurately you need to measure, GPS satelites have to correct for relativity but the effect is tiny.

 

[Sonko]

ok well let's say i was to measure the velocity of a small mass particle and one with a larger mass in the lab frame (lets say an electron and proton). if both particle were to have the same wavelength and so same energy would i be correct in saying that due to their sizes it would be appropriote to include relativistic effects on the electron, but not nessasary for the proton within a good accuracy?