The linear momentum and position vector of the planet is perpendicular to each other at

(a)

perihelion and aphelion

(b)

at all points

(c)

only at perihelion

(d)

no point

The gravitational potential energy of the Moon with respect to Earth is

(a)

always positive

(b)

always negative

(c)

can be positive or negative

(d)

always zero

The work done by the Sun’s gravitational force on the Earth is

(a)

always zero

(b)

always positive

(c)

can be positive or negative

(d)

always negative

The magnitude of the Sun’s gravitational field as experienced by Earth is

(a)

same over the year

(b)

decreases in the month of January and increases in the month of July

(c)

decreases in the month of July and increases in the month of January

(d)

increases during day time and decreases during night time

If a person moves from Chennai to Trichy, his weight

(a)

increases

(b)

decreases

(c)

remains same

(d)

increases and then decreases

State Newton’s Universal law of gravitation.

Why is there no lunar eclipse and solar eclipse every month?

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?

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?

Discuss the important features of the law of gravitation.

Derive the expression for gravitational potential energy.

Explain the variation of g with depth from the Earth’s surface.