EART160 – EXAMPLE FINAL QUESTIONS
SHORT ANSWERS
Name four Solar system bodies that have dunes (2)
A 50km diameter crater has been extended by 1km due to normal faulting. If the Young’s
modulus is 100 GPa, how big were the tectonic stresses? (2)
How long does it take a dike 5 km high and 2m thick to cool? (2)
Give two ways in which some extra-solar planets are very different from the giant planets
in our solar system (2)
Give two reasons why big terrestrial planets tend to be hotter inside than small terrestrial
planets (2)
Write down the orbital angular momentum of a satellite in terms of its mass m, orbital
frequency
, G and the mass of the primary M (2)
LONG ANSWERS
a) Using the hydrostatic assumption and the ideal gas law, show that the variation of
pressure in an isothermal atmosphere is given by P=P0 exp(-z/H), where P0 is the surface
pressure and H is the scale height (4)
b) Also write down an expression for how the density
varies with height, in terms of the
density at the surface
0 (1)
c) Use your answer to b) to derive an expression for the total mass contained in a column
of atmosphere of surface area 1m2 in terms of
0 and H (3)
d) Now express your answer to c) in terms of P0 and the gravity g (1)
e) Write down an expression for the total mass of atmosphere contained on a planet in
terms of P0,g and R, the radius of the planet (1)
f) If this atmosphere is being heated by solar power S (in Watts), write down an
expression for the time t it takes for the entire atmosphere to heat up by 1K in terms of
P0,g,R,S and Cp, the specific heat capacity of the gas (2)
g) Describe how this time changes as P0 and Cp change, and explain why these effects
make physical sense (2)
g) For the Earth, we have P0=105 Pa, g=10 ms-2, R=6400 km, S=3x1017 W, Cp=300 Jkg-1
K-1. What is the time t? (1) (15 total)
