Wednesday, December 23, 2015

fluid dynamics - Will the box move if I blow air inside it?


Suppose that I have a box in space and it is filled with air in it. I keep a fan at one end and blew the air to other end. The air will hit the box with some velocity, so it should move.


I know that this is completely false because the momentum of the system remains constant. But somehow I cannot explain that clearly.


Fan in box




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