Which of the following sequences correctly describes the stages of life for a low-mass star?
A) protostar, red giant, main-sequence, white dwarf
B) protostar, main-sequence, white dwarf, red giant
C) white dwarf, main-sequence, red giant, protostar
D) protostar, main-sequence, red giant, white dwarf
E) red giant, protostar, main-sequence, white dwarf
D
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The 
Al nucleus is unstable. To what will it decay?
A. 
B. 
C. 
D. 
E. Other (specify)
Each of the following lists two statements. Which two are the basic premises for the special theory of relativity?
A) (1) The laws of nature are the same for everyone. (2) The speed of light is the same for everyone. B) (1) The laws of nature are relative. (2) The speed of light depends on your viewpoint. C) (1) You can't go faster than the speed of light. (2) Time is different for different people. D) (1) Everything is relative. (2) You can never really tell who is moving.
If we could combine all the planets together, their total mass would be about ________ the Sun's mass.
A) 1/1000 of B) 1/10 of C) the same as D) double E) half of
Two 1.5 m-square and parallel flat plates are 30 cm apart. Plate A1 is maintained at a temperature of 1100 K and A2 at 500 K. The emissivities of the plates are 0.5 and 0.8, respectively. Considering the surroundings black at 0 K and including multiple inter-reflections, determine (a) the net radiant exchange between the plates and (b) the heat input required by surface A1 to maintain its temperature. The outer-facing surfaces of the plates are adiabatic.
GIVEN
• Two square parallel flat plates, 30 cm apart
• Temperature of A1 (T1) = 1100 K
• Temperature of A2 (T2) = 500 K
• Emittances: ?1 = 0.5 ?2 = 0.8
• Surroundings are black at (T3) = 0 K
FIND
Including multiple inter-reflections, determine:
(a) The net radiant exchange (q1–2)
(b) The heat input at surface A1 (q1) required to maintain its temperature
SKETCH
PROPERTIES AND CONSTANTS
the Stephan-Boltzmann constant (?) = 5.67 × 10–8 W/(m2 K4)