[填空题]
The escape speed from the Earthn3yit8m1 b(uxeid wg7p ;z7+h ixmsdcjne/,5lo3 8k)m s $ 1.12\times10^{4 } m/s$ so a gas molecule travelling away from Earth near the outer boundary of the Earth’s atmosphere would, at this speed, be able to escape from the Earth’s gravitational field. At what temperature is the average speed of
(a) oxygen molecules, $ \times10^{5 }$K
(b) helium atoms equal to $ 1.12\times10^{4 } m/s$ $ \times10^{4}$K
(c) Can you see why our atmosphere contains oxygen but not helium?
