IIT JEE , AIEEE Forum - Physics , Thermal Physics - KINETIC THEORY OF GASES....... HCV related doubt

biki

open HCV - 2 chapter - Kinetic Theory of Gases .........

Now in the assumptions of KTG .. the last assumption is explained by taking examples........ i have a problem there...

the first example is clear...

in the second example, it says that, for a gas, if there are 400 molecules in 1cm³ having velocity along x-direction , then there will be 400 molecules in some other 1cm³ having velocity along x-direction. (upto here, its clear)

Then it says, that also there will be 400 molecules in 1cm³ having velocity along y-direction.

This the centre of confusion.

Does existence of 400 molecules having velocity along x-direction in 1cm³ of a gas imply that there will be exactly 400 molecules having velocity along y-direction in 1cm³ of the gas ?????

If yes,then how can we conclude ???... there is no mention about this in the assumptions of KTG.

If no, then why does the book say so ??...

rooney

If suppose n things are similar in ALL aspects, we assume that they will be similar in any one other aspect as well. Something like, if 1 Human has 2 kidneys, we assume that any chosen human will also have 2 kidneys (this is called generalisation).

Now, x ,y and z axis are similar in ALL their properties/aspects. So, all their properties are taken to be same as well. Thats why 400 molecules in 1 cm3 of air are moving in x , y (and z though it doesnt seem to be mentioned) directions.

biki

does it mean 1200 molecules/cm ^3 ??????????

please answer it.......... and i'll close the topic !!!!

rooney

Yes you are right.

nikss

as momemtem is conserved in all directions.........

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