RMS speed when doubling gas molecules at constant volume and pressure

[lbumbalo]

Homework Statement

An ideal gas is kept in a container of constant volume. The pressure of the gas is also kept constant. The number of molecules in the gas is doubled. If the initial rms speed is 1300m/s, what is the final rms speed?

Homework Equations

Vrms=sqrt[(3kT)/m]
PV=NkT

The Attempt at a Solution

I've tried to rework the above equations hoping I would find something but there seem to be too many unknowns. I know that you need to lower the temperature of the gas, but I'm not given the initial temp or the final, and I don't know the initial number of molecules. Thanks

 

[Andrew Mason]

Homework Statement

An ideal gas is kept in a container of constant volume. The pressure of the gas is also kept constant. The number of molecules in the gas is doubled. If the initial rms speed is 1300m/s, what is the final rms speed?

Homework Equations

Vrms=sqrt[(3kT)/m]
PV=NkT

The Attempt at a Solution

I've tried to rework the above equations hoping I would find something but there seem to be too many unknowns. I know that you need to lower the temperature of the gas, but I'm not given the initial temp or the final, and I don't know the initial number of molecules. Thanks

Express the initial T in terms of the other variables. If PV is kept constant and N is doubled, what happens to T?

AM