A body weighs \(72~\text{N}\) on the surface of the earth. What is the gravitational force on it at a height equal to half the radius of the earth?

1.	\(32~\text{N}\)	2.	\(30~\text{N}\)
3.	\(24~\text{N}\)	4.	\(48~\text{N}\)

What is the depth at which the value of acceleration due to gravity becomes 1/n times the value of that at the surface of the earth? (radius of earth = R)

(1) R/${\mathrm{n}}^2$

(2) R(n – 1)/n

(3) Rn/(n – 1)

(4) R/n

Choose the correct alternative.

Acceleration due to gravity is:

Suppose there existed a planet that went around the sun twice as fast as the Earth. Then its orbital size as compared to that of the Earth would be:

One of the satellites of Jupiter has an orbital period of \(1.769\) days and the radius of the orbit is \(4.22 \times 10^{8}\) m. The ratio of the mass of Jupiter and the mass of the sun nearly is: (Mass of the sun \(\approx 2\times 10^{30}~\text{kg}\))
1. \(1000:1\)
2. \(1:1000\)
3. \(1:1\)
4. \(2000:3\)

Choose the correct alternative.

Let us assume that our galaxy consists of 2.5 × ${10}^{11}$ stars each of one solar mass. How long will a star at a distance of 50,000 ly from the galactic centre take to complete one revolution? (The diameter of the milky way is ${10}^5$ ly.)
1. 3.55 × 10⁸ years
2. 4.55 × 10⁸ years
3. 3.55 × 10⁷ years
4. 4.55 × 10⁷ years

The escape speed of a body from the Earth depends on:

A comet orbits the sun in a highly elliptical orbit. The comet has a constant:
1. linear speed
2. angular speed
3. angular momentum
4. kinetic energy