Q1. Solar eclipse occurs when
(a) Earth comes between sun and moon
(b) Moon is at right angle to the earth
(c) Moon comes between sun and earth
(d) Sun comes between moon and earth
(UPSC Prelims 1979)
Answer: (c) Moon comes between sun and earth
Explanation: A solar eclipse takes place when the Moon moves directly between the Sun and the Earth, causing the Sun’s light to be blocked either partially or completely. This alignment leads to the Moon casting a shadow on Earth, and the eclipse is visible only from specific regions where this shadow falls. The Moon must be in its new moon phase for this phenomenon to occur.
Q2. When a man circles round the earth in a satellite, then
(a) His mass becomes zero but weight remains constant
(b) Mass remains constant but weight becomes zero
(c) Both mass and weight remain constant
(d) Both mass and weight remain zero
(UPSC Prelims 1979)
Answer: (b) Mass remains constant but weight becomes zero
Explanation: In a satellite orbiting Earth, a person experiences weightlessness due to the free-fall condition of orbit. While mass is an intrinsic property and remains unchanged, weight depends on gravitational force. In orbit, the person is in continuous free fall, which results in zero apparent weight, even though gravity is still acting.
Q3. The weight of an object at the poles is greater than at the equator. This is because
(a) Of the shape of the earth
(b) The attraction of the moon is maximum at the earth’s surface
(c) The attraction of the sun is maximum at the earth’s surface
(d) Gravitational pull is more at the poles
(UPSC Prelims 1979)
Answer: (d) Gravitational pull is more at the poles
Explanation: The Earth is not a perfect sphere; it is slightly flattened at the poles and bulging at the equator. This shape causes the distance from the center of the Earth to the poles to be less than to the equator. As a result, the gravitational force is stronger at the poles, making the weight of objects greater there.
Q4. The minor planets revolving between the orbits of Mars and Jupiter are called
(a) Asteroids
(b) Comets
(c) Meteors
(d) Novas
(UPSC Prelims 1979)
Answer: (a) Asteroids
Explanation: Asteroids are small rocky bodies that orbit the Sun, primarily found in the asteroid belt between Mars and Jupiter. They are considered minor planets and differ from comets, which contain ice and dust.
Q5. The planets nearest to Sun are
(a) Mercury and Mars
(b) Earth and Mercury
(c) Mercury and Venus
(d) Mercury and Uranus
(UPSC Prelims 1979)
Answer: (c) Mercury and Venus
Explanation: Mercury is the closest planet to the Sun, followed by Venus. Their proximity results in high surface temperatures, and they orbit the Sun faster than other planets due to strong gravitational pull.
