If c̅, C and α represent the mean velocity, root mean square velocity and the most probable velocity of a gas at a temperature T then: 

CONCEPT:

Mean velocity of the gas

• Mean velocity is the arithmetic mean of the velocities of different molecules of a gas at a given temperature.
• It is given as,

Root mean square velocity of the gas

• Root mean square velocity (RMS value)is the square root of the mean of squares of the velocity of individual gas molecules.
• It is given as,

​

The most probable velocity of a gas

• The most probable velocity at which the most molecules in gas travel.

• It is given as,

​EXPLANATION:

• From the formula of the above three velocities of the gas at a particular temperature, it is clear that,

⇒ α < c̅ < C

• Hence, option 4 is correct.