JEE Advanced 2017 Physics question

A flat plate is moving normal to its plane through a gas under the action of a constant force . The gas is kept at a very low pressure. The speed of the plate is much less than the average speed of the gas molecules. Which of the following options is/are true?

(A)The pressure difference between the leading and trailing faces of the plate is proportional to Correct
(B)The resistive force experienced by the plate is proportional to Correct
(C)The plate will continue to move with constant non-zero acceleration, at all times
(D)At a later time the external force balances the resistive forceCorrect

Answer: (A),(B),(D)

Solution

At very low pressure the molecules strike the plate independently. Relative to the plate, molecules hit the leading face with speed about and the trailing face with speed about ; the pressure on a face is proportional to . So , proportional

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Question ID VK-026592