Average Molecular Speed

[@zulqarnainchaughtai]

Why do we need different types of speed in the first place? Why isn't average speed sufficient, and why do we define mean square or root mean square speed?

[@PhysicalChemistry]

Good question! They're all useful in different circumstances. Speed is proportional to momentum, for example, while squared speed (or velocity) is proportional to KE and temperature. So mean square speed tells us something closer to the average KE or temperature. But squared-speed doesn't have units of speed or velocity, so we often use rms velocity when we want to think about it as a speed.

[@zulqarnainchaughtai]

@PhysicalChemistry Thanks a lot. When will your own book get published?

[@PhysicalChemistry]

@@zulqarnainchaughtai I have to finish writing it first. 🙂

[@dysprosiumdead5078]

phenomenal explanation@@PhysicalChemistry

[@dysprosiumdead5078]

connects so well to everything @@PhysicalChemistry

[@cristheltorres7354]

thank you😊

[@chiranjeevirachapalli899]

Thank You sir, You never disappoint !! By the way wich physical chemistry book is worth buying and reading along with your lectures sir !!

[@PhysicalChemistry]

I usually recommend the book by McQuarrie and Simon. (Or my own book, but only my students have access to that for now.)

[@miglelenkauskaite6207]

Thank you so much!!

[@PhysicalChemistry]

You're welcome!

[@xohellocutie]

in what video did you calculate v^2?

[@PhysicalChemistry]

The previous calculation I referred to was done in the video title Root Mean Square Velocity (kzbin.info/www/bejne/onmzeaiYmquhrZI) Whenever I mention something from a previous video, keep an eye out for the "Suggested Video" card that pops up in the upper right. That's always a link to the earlier video that I mention.

[@xohellocutie]

@@PhysicalChemistry thank you!

[@MahirahUlfahAbdi-be9sj]

How much for pi

[@PhysicalChemistry]

3.14159265...

[@jerilgeorgejacob1136]

3.141592653589793238462643.......

[@jerilgeorgejacob1136]

3.141592653589793238462643.......

[@mortezakhoshbin]

thanks god nitrogen molecules average velocity is zero in other case the life would be difficult by pushing molecules from one side in front or back of people hahahaa. thanks dr stuart you are amazing

[@PhysicalChemistry]

I guess it depends... if you were moving with them it might make your life easier. :-) But of course we do need to push molecules out of the way: that is air resistance.

[@mysteriousness347]

❤❤