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Physics 002 Final Examination 23 May, 2002.
Time allowed: 90 minutes Total: 70 marks
Name:
Student ID:
A
Data table:
1 parsec
3.26 light years
Speed of light
300,000 km/s
Universal gravitational constant
6.67 10-11 N.m2/kg2
1 Astronomical Unit
1.50 1011 m
Mass of Sun
1.99 1030 kg
Hubble constant
70 km/s/Mpc
Our distance from the center of Milky Way
8,500 pc
Part A Multiple choice (16 marks):
(1) It is observed that in a binary system, the giant star is less massive, but the main-sequence star is more massive. This does not agree with the expectation that massive stars normally evolve faster than less massive ones, possibly because:
A.
matter is lost in the form of radiation.
B.
matter falls onto the accretion disk surrounding a compact object.
C.
the less massive star is originally more massive, but matter is transferred to its companion star when it became a giant.
D.
the less massive star is originally more massive, but type I supernova explosions blow its matter away.
E.
the less massive star is originally more massive, but nova explosions blow its matter away.
Ans: C
This is called the Algol paradox. See the discussion of the evolution of closed binary systems in Lecture 19, or pp. 284-285 in the textbook.
(2) According to the theory of relativity,
A.
muons through the atmosphere appear to decay faster than those observed on Earth.
B.
the elliptical orbit of Mercury is distorted to a circle when viewed from the Earth.
C.
the orbital size of binary pulsars increases with time.
D.
distant starlight appears bluer to an observer near the event horizon of a black hole.
E.
distant stars appear in directions closer to the Sun during solar eclipses.
Ans: D
Choice A contradicts time dilation.
Choice B is ridiculous.
Choice C contradicts to the emission of gravitational waves.
Choice D is the reverse effect of gravitational redshift when light travels towards a black hole, and is therefore correct.
Choice E contradicts the inward direction of light bending by Suns gravity.
(3) Which of the following will happen in a critical universe?
A.
The density of the universe will always be a constant.
B.
The Hubble constant will increase in the future.
C.
A Big Crunch will occur some time in the future.
D.
The expansion of the universe will continue forever.
E.
The expansion of the universe will accelerate.
Ans: D
Choice A: The density will continue to decrease when the universe expands.
Choice B: Since velocity will decrease and distance will increase, the Hubble constant will decrease in the future.
Choice C: A Big Crunch occurs only in a close universe.
Choice D and E: The expansion of the universe will continue forever, although it will slow down indefinitely.
(4) How