Question

The relationship between velocity(U) of a gas molecules and their relative molecular mass(RAM) is?

Answer 1

Isn't this available in your notes/text?
http://www.chemteam.info/GasLaw/gas-velocity.html

Answer 2

just use v(rms) = (158)[SqrRt(T/M)] meters/sec ... T = Kelvin & M = gms/mole ... 158 is from SqrRt[(3)(8.314)(1000)] ... These are constants factored out of the original equation v(rms) = SqrRt(3RT/M).