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Question
Which of the following quantities is zero on an average for the molecules of an ideal gas in equilibrium?
Options
Kinetic energy
Momentum
Density
Speed
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Solution
Momentum
The molecules move in all possible directions in an ideal gas at equilibrium. Since momentum is a vector quantity for every direction of motion of the molecules, there exists an opposite direction of motion of the other. Hence, the average momentum is zero for an ideal gas at equilibrium.
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