If four molecules of a gas have speed 2, 4, 6, 8 kms^-1 respectively, then root mean square speed (in kms^-1) will be .. and respectively.

Here, ${\mathrm{c}}_1=2{\mathrm{kms}}^{-1};{\mathrm{c}}_2=4{\mathrm{kms}}^{-1}$

          ${\mathrm{c}}_3=6{\mathrm{kms}}^{-1}\text{ and }{\mathrm{c}}_4=8{\mathrm{kms}}^{-1}$

,

               

 Root mean square speed,

                  $\begin{array}{c}\mathrm{c}=\sqrt{\frac{{\mathrm{c}}_1^2+{\mathrm{c}}_2^2+{\mathrm{c}}_3^2+{\mathrm{c}}_4^2}{4}}=\sqrt{\frac{2^2+4^2+6^2+8^2}{4}}\\ =5.48{\mathrm{kms}}^{-1}\end{array}$