The density of a newly discovered planet is twice that of earth. The acceleration due to

gravity at the surface of the planet is equal to that at the surface of the earth. If the

radius of the earth is R, the radius of the planet would be

1. 2R                   

2. 4R

3. $\frac{1}{4}R$               

4. $\frac{1}{2}R$     

If R is the radius of the earth and g the acceleration due to gravity on the earth's surface,

the mean density of the earth is:

1. $4\pi G/3gR$                                 

2. $3\pi R/4gG$

3. $3g/4\pi RG$                               

4.$\pi RG/12G$        

A planet has twice the radius but the mean density is $\frac{1}{4}th$ as compared to earth. What is the ratio of escape velocity from earth to that from the planet ?

1. 3:1                                                                 

2. 1:2

3. 1:1                                                                 

4. 2:1

A body weighs 500 N on the surface of the earth. How much would it weigh halfway

below the surface of the earth?

1. 125 N                               

2.  250 N

3. 500 N                               

4.  1000 N

Who among the following gave first the experimental value of G?

1. Cavendish                               

2. Copernicus

3. Brook Taylor                           

4. None of these

3 particles each of mass m are kept at vertices of an equilateral triangle of side L. The

gravitational field at centre due to these particles is

1. zero                                                                       

2. $\frac{3GM}{L^2}$

3. $\frac{9GM}{L^2}$                                                                     

4. $\frac{12}{\sqrt{3}}\frac{GM}{L^2}$

The weight of an object in the coal mine, sea level, at the top of the mountain are  $W_1$,

$W_2$ and $W_3$   respectively, then

1.  $W_1\le W_2\ge W_3$                      

2.  $W_1=W_2=W_3$

3.  $W_1\le W_2\le W_3$                     

4.  $W_1\ge W_2\ge W_3$      

The value of escape velocity on a certain planet is 2 km/s. Then the value of orbital speed

for a satellite orbiting close to its surface is:

1. 12km/s                                                                 

2. 1km/s

3. $\sqrt{2 } km/s$                                                             

4. $2\sqrt{2} km/s$

Four particles each of mass M, are located at the vertices of a square with side L. The

gravitational potential due to this at the centre of the square is

1. $-\sqrt{32}\frac{GM}{L}$                                   

2. $-\sqrt{64}\frac{GM}{L^2}$

3. zero                                             

4. $\sqrt{32}\frac{GM}{L}$

The mass of the moon is $7.34\times {10}^{22}kg$ and the radius is $1.74\times {10}^{6}m$. The value of

gravitation field will be

1. $1.45 N/kg$                               

2. $1.55 N/kg$

3. $1.75 N/kg$                               

4.  $1.62 N/kg$