If both the mass and the radius of the earth is decreased by \(1\%\), then the value of the acceleration due to gravity will:

1.	decrease by \(1\%\)	2.	increase by \(1\%\)
3.	increase by \(2\%\)	4.	remain unchanged

The earth (mass = $6\times {10}^{24}kg$ ) revolves round the sun with angular velocity

$2\times {10}^{‐7}rad/s$ in a circular orbit of radius $1.5\times {10}^{8}km$ . The force exerted by the sun on

the earth in Newtons, is

1. $18\times {10}^{25}$                               

2. Zero

3. $27\times {10}^{39}$                               

4. $36\times {10}^{21}$

The gravitational force between two point masses $m_1$  and $m_2$  at separation r is given by $F=k\frac{m_1{m}_2}{r^2}$  The constant k                                                                

1. Depends on system of units only

2. Depends on medium between masses only

3. Depends on both 1 and 2

4. Is independent of both 1 and 2

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

The distance between the centres of moon and earth is D. The mass of earth is 81 times the mass of the moon. At what distance from the centre of the earth the gravitational force will be zero?

1. $\frac{D}{2}$                               
2. $\frac{2D}{2}$                                
3. $\frac{4D}{3}$                             
4. $\frac{9D}{10}$

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. $\frac{12}{\sqrt{3}}\frac{GM}{L^2}$