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Physics 002 Final Examination 21 December 2004
Time allowed: 180 minutes Total: 140 marks

Name:

Student ID:

Seat:
A




Section
Marks

A


B


C


D1


D2


D3


D4


Total





Table 1: Useful Data

1 parsec
3.26 light years

1 parsec
206,265 AU = 3.085678x1016m

1 Astronomical Unit
1.50 1011 m

Speed of light
3.0 108 m/s

Universal gravitational constant
6.67 10-11 N.m2/kg2

Mass of the Sun MSun
1.99 1030 kg

Apparent magnitude of the Sun
-26.74

Absolute magnitude of the Sun
4.8

1 solar radius
6.9599 108 m

Mass of the Earth
5.976 1024 kg

Radius of the Earth
6.378164 106 m





Section A: Multiple Choice (20 marks)

(1) By a stars position on an H-R diagram alone, we can determine its
A. age, luminosity, and distance
B. age, chemical composition, and luminosity
C. luminosity, surface temperature, and size
D. color, mass, and chemical composition
E. distance, apparent brightness, and mass
Ans. __C____

(2) The Chandrasekhar limit is the mass of a star in which
A. gravity overcomes the electromagnetic repulsion of electrons
B. gravity overcomes the degenerate neutron pressure
C. gravity overcomes the degenerate electron pressure
D. gravity overcomes the radiation and gas pressure
E. gravity overcomes the nuclear force
Ans. ___C___


(3) The Hubble expansion is not particularly noticeable for nearby galaxies in our local cluster because
A. The Hubble expansion was only significant in an early phase of the universe, and has slowed down to almost unnoticeable today.
B. We cannot accurately measure distances to nearby galaxies, and so we cannot tell if they are receding from us or not.
C. The motion of the Earth around the Sun makes it impossible to detect the Hubble expansion of nearby galaxies
D. The motions of individual galaxies within our local cluster is much
larger than the local effects from the Hubble expansion
E.
Our galaxy resides in a void, or local pocket, that is not expanding as

fast as the rest of the universe.
Ans. __D____




(4) How can astronomers detect the presence of a black hole?
1. by the light we receive from the black hole itself
2. by the x-rays we receive from an accretion disk of matter falling into the
black hole
3. by observing the blue shift of the rear light of a spaceship moving
toward a black hole
4. by its gravitational influence on a companion star or other objects
A. 1 and 2 only
B. 2 and 3 only
C. 3 and 4 only
D. 1 and 3 only
E. 2 and 4 only
Ans. ___E___

(5) The current astronomical theory implies that the distance of the Earth from the center of the universe (location of the Big Bang) is
A. equal to the age of the