=========================preview======================
(PHYS002)finala_s02.pdf
Back to PHYS002 Login to download
======================================================
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
3 108 m/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):

Question
(1)
(2)
(3)
(4)

Answer








(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.




(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.




(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.




(4) How do supernova explosions affect their host galaxy?
$1: They increase the amount of heavy elements in the interstellar cloud.
$2: They facilitate the formation of stars.
$4: They make the galactic space dusty.
$8: They make their host galaxy reddish in colour.
After adding up the dollar values of the correct answers, what is the total value?


Part B Short Questions. Give your numerical answers to 2 significant figures. (18 marks):

(1-2) Suppose the Hubble constant is 65 km/s/Mpc (instead of the value in the data table).
(1) What is the age of the Universe if we assume that there is no gravity? Give your answer in billion years.


(2) What is the age of the Universe if we assume that the Universe is flat? Give your answer in billion years.







N