Distribution in given direction

Maxwell s distribution law states that the fraction of molecules of mass in a given volume having a velocity in a given direction between u and u- - du)s 

The fraction of molecules in a given volume having kmetic energy of motion in a given direction exceeding E = mU is 

The fraction of molecules crossing (or hitting) a given plane having kinetic energy normal to this plane exceeding E = JwCT is 

The reason that the answer to (b) is greater than the answer to (a) is that faster molecules cross a plane more frequently than slower ones. 

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