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(PHYS002)midterm_a_sol_f05.pdf
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PHYSICS 002
Midterm
Date: 15 October 2005
Time allowed: 120 minutes
Total: 124 marks


Name:

Student ID:

Seat:
A




Section
Marks

A
40

B
20

C:P1
20

C:P2
22

C:P3
22

Total
124





Table 1: Useful Data

1 parsec
3.26 light years

1 parsec
206,265 AU

1 radian
206,265 arc seconds

1 Astronomical Unit
1.5 108 km

Speed of light
3 108 m/s

Mass of the Sun (MSun)
1.99 1030 kg

Apparent magnitude of the Sun
-26.8

Absolute magnitude of the Sun
4.83



Section A: Multiple choice (40 marks total, 4 marks each)

(1) What makes the North Star (Polaris) special?

A.
It was the first star to be cataloged by ancient astronomers.


B.
It lies close to the north celestial pole and is therefore very useful for navigation.


C.
It is the brightest star in the entire sky.


D.
It is the brightest star in the northern sky.


E.
It is visible from both the northern and southern hemispheres.

Ans. ___B___



(2) At the Summer solstice, the noon Sun at a city in Northern hemisphere has an angle of elevation of 90o to the South. At the Winter solstice, the angle of elevation of the noon Sun at the city becomes.. to the South.

A.
23.5o


B.
43 o


C.
66.5o


D.
90 o


E.
113.5 o Ans. ___B___




Explanation:
At the Summer solstice, the noon Sun has an angle of elevation higher than the latitude by 23.5o. Hence the latitude of the city is 90o C 23.5o = 66.5o.
At the Winter solstice, the noon Sun has an angle of elevation lower than the latitude by 23.5o. Hence the angle is 66.5o C 23.5o = 43o.

(3) If Earths orbit were a perfect circle, we would not have seasons.

A.
Correct, because the Earth would be at the same distance from the Sun throughout its orbit, there would be no summer or winter.


B.
Correct, it is the deviations from a circular orbit that create the seasons.


C.
False, the seasons are due to the tilt of the Earths axis, not its distance from the Sun.


D.
False, the poles would still be cooler than the equator and seasonal variations would therefore still exist.


E.
False, whether circular or not, the seasons depend on the precession of the Earths axis as it orbits the Sun.



Ans. __C____
(4) According to Newton,

A.
The gravitational force of Earth acting on the Moon has the same magnitude as that acting on an apple on the surface of Earth.


B.
The gravitational acceleration of the Moon towards Earth is the same as that of an apple falling towards Earth on the surface of Earth.


C.
The gravitational acceleration of the Moon towards Earth is the same as that of an apple moving on the orbit of the Moon. The gravitational acceleration of the Moon towards Earth is the same as that of an apple moving on the orbit of the