# Explain why the average velocity of the gas molecules in a container is zero

Hey there guys i am new here and not sure if this is in the right section, well here goes.

Just doing some revision and realised I must have been asleep for the Kinetic theory lessons, i have now grasped some of the basics, but have come to this question and not usre how to answer it....

Explain why the average velocity of the gas molecules in a container is zero.

Now i have had a look around on wikipedia and things like that but it goes into a lot of detail, and we dont need to go into that much detail, also I dont just want the answer handed to me i would appreciate it if you could explain it for me in fairly simple terms...

Many Thanks

Joe

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Doc Al
Mentor
Hint: What's the difference between velocity and speed?

velocity is a vector quantity and therfore has a direction aswell as the speed...

so because this is the mean square velocity, does that mean as the molecules are boucing off the walls all the time then their velocities are cancelling each other out because as it hits at 500m/s it then rebounds at -500m/s or something along those lines?

ooo wait squaring it, that will change it from being negative to postive....

Doc Al
Mentor
so because this is the mean square velocity...