Conceptual Questions Answers

Physics : Gravitation

Conceptual Questions

1. In the following, what are the quantities which that are conserved?

a) Linear momentum of planet

b) Angular momentum of planet

c) Total energy of planet

d) Potential energy of a planet

Answer: (b & d) Angular momentum of planet, Potential energy of a planet]

2. The work done by Sun on Earth in one year will be

a) Zero

b) Non zero

c) positive

d) negative

[ Answer: (a) zero]

3. The work done by Sun on Earth at any finite interval of time is

a) positive, negative or zero

b) Strictly positive

c) Strictly negative

d) It is always zero

[Answer: (d) It is always zero]

4. If a comet suddenly hits the Moon and imparts energy which is more than the total energy of the Moon, what will happen?

Answer

If a comet hits the moon with large mass and with large velocity may destroy the moon completely or its impact makes the moon, go out of the orbit.

5.  If the Earth’s pull on the Moon suddenly disappears, what will happen to the Moon?

Answer

If the gravitational force suddenly disappears, moon will stop revolving around the earth and it will move in a direction tangential to its original orbit with a speed with which it was revolving around the earth.

6.  If the Earth has no tilt, what happens to the seasons of the Earth?

Answer

If the Earth has no tilt, there will be no seasons like now and the duration of day and night \vi! be equal throughout the year.

7.  A student was asked a question ‘why are there summer and winter for us? He replied as ‘since Earth is orbiting in an elliptical orbit, when the Earth is very far away from the Sun(aphelion) there will be winter, when the Earth is nearer to the Sun(perihelion) there will be winter’. Is this answer correct? If not, what is the correct explanation for the occurrence of summer and winter?

Answer

No, The seasons in the Earth arise due to tit; rotation of Earth around the Sun with 23.5° tilt Due to this 23.5° tilt, when the northern parto Earth is farther to the Sun, the southern part: nearer to the Sun. So when it is summer in tb northern hemisphere, the southern hemisphet experience winter.

8.  The following photographs are taken from the recent lunar eclipse which occurred on January 31, 2018. Is it possible to prove that Earth is a sphere from these photographs?

Answer

No. The moon goes around the earth in an elliptical orbit. This means its distance from us varies periodically as it goes around us.