# Astronomy college course/Why planets lose their atmospheres/Quiz/Original version of this quiz

1 It is important to distinguish between molecules (collectively) in a gas and one individual molecule. This question is about an individual molecule. For a planet with a given mass, size, and density, which has the greater escape velocity?

 the heavier molecule has the greater escape velocity the lighter molecule has the greater escape velocity all molecules have the same escape velocity no molecules have escape velocity all molecules move at the escape velocity

2 It is important to distinguish between molecules (collectively) in a gas and one individual molecule. This question is about a typical molecule in the gas. For a planet with a given mass, size, and density, which type of gas is more likely to escape?

 atoms in a hotter gas is more likely to escape atoms in a denser gas are more likely to escape atoms in a gas with more atomic mass are more likely to escape all types of gas are equally likely to escape atoms in a colder gas are more likely to escape

3 Which type of gas is likely to have the faster particles?

 a hot gas with low mass atoms a hot gas with high mass atoms a cold gas with low mass atoms a cold gas with high mass atoms all gasses on a given planet have the same speed

4 What is it about the isotopes of Argon-36 and Argon-38 that causes their relative abundance to be so unusual on Mars?

 different half-life different speed different chemical properties identical mass identical abundance

5 In the formula, ${\displaystyle {\frac {1}{2}}m_{\mathrm {atom} }v_{\mathrm {escape} }^{2}=G_{\mathrm {Newton} }{\frac {M_{\mathrm {planet} }m_{\mathrm {atom} }}{r_{\mathrm {planet} }}}}$, which of the following is FALSE?

 vescape is independent of matom the formula is valid for all launch angles the formula is valid only if the particle is launched from the surface of planet of radius rplanet the formula can be used to estimate how fast an atom must move before exiting the planet the particle is assumed to have been launched vertically

6 What statement is FALSE about ${\displaystyle {\frac {1}{2}}m_{\mathrm {atom} }\langle v_{\mathrm {atom} }^{2}\rangle _{ave}={\frac {1}{2}}k_{\mathrm {B} }T}$?

 The kinetic energy is directly proportional to temperature. The average speed of a low mass particle is higher than the average speed of a high mass particle Temperature is measured in Kelvins Temperature is measured in Centigrades This equation does not involve the size or mass of the planet.

7 ${\displaystyle {\frac {1}{2}}m_{\mathrm {atom} }\langle v_{\mathrm {atom} }^{2}\rangle _{ave}={\frac {1}{2}}k_{\mathrm {B} }T}$, where T is temperature on the Kelvin scale. This formula describes:

 The speed an atom needs to escape the planet, where m is the mass of the atom. The speed of a typical atom, where m is the mass of the atom. The the speed an atom needs to escape the planet, where m is the mass planet. The speed of a typical atom, where m is the mass of the planet. The speed an atom needs to orbit the planet, where m is the mass of the atom.