- #1

Derek1997

- 63

- 1

## Homework Statement

There is almost no helium gas in the earth’s atmosphere - indeed the price of He has increased in

recent times due to worries about a limited supply. (Bad news for parties and for all the scientists

who use liquid He as a coolant.) we know that the “escape velocity” required

to escape from the earth’s gravitational field is ⇠11.2km/s. Explain using physical concepts,

and kinetic theory in particular, why there is very little He gas in the atmosphere. Start by

calculating the root mean square (rms) speed of Helium (He) gas in the upper atmosphere,

assuming a temperature of 2000 K. Note that the atomic weight of He' 4, where 1 atomic mass

unit = 1.67 ⇥ 10−27kg

## Homework Equations

v=sqrt(3kt/m

## The Attempt at a Solution

I did the equation since we were given K is constant 1.38x10^-23 J/k i subbed the value inside and I got

v=sqrt(3(1.38x10^-23)(2000)/6.644x10^-27) Note I did find mass using mm and avogardos number. I got number of 3530.2m/s and escape velocity is in km/s that is if it converted to m/s it's way higher than the velocity calculated which doesn't make sense. I expected velocity to be higher... any help is appereciated :)