# Gas Speed Problem

1. Feb 28, 2005

### R.Harmon

"The composition of planetary atmospheres is determined in part by the speeds of the molecules of the constituent gases, because the faster moving molecules can reach escape velocity and leave the planet. Calculate the r.m.s. speed in meters per second of helium species at a temperature of 361 Kelvin."

Right, I have absolutely no idea where to start with this problem, so any formulas or guidance as to how to solve this would be greatly appreciated.

Thanks.

2. Feb 28, 2005

### stunner5000pt

depeding on the course you're taking you should have done thermodynamics

$$v_{rms} = \sqrt{\frac{3RT}{M}}$$
where R is the universal gas constant, T is the temperature and M is the molar mass of the atoms involved.