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 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. $1.45<mspace\; width="1em"></mspace>N/kg$                               

2. $1.55<mspace\; width="1em"></mspace>N/kg$

3. $1.75<mspace\; width="1em"></mspace>N/kg$                               

4.  $1.62<mspace\; width="1em"></mspace>N/kg$

Which one of the following graphs represents correctly the variation of the gravitational field (I) with the distance (r) from the centre of a spherical shell of mass M and radius a ?

1.		2.
3.		4.

Suppose, the acceleration due to gravity at the earth’s surface is 10 $\mathrm{m}/{\mathrm{s}}^2$ and at the surface of Mars, it is 4.0 $\mathrm{m}/{\mathrm{s}}^2$. A 60 kg passenger goes from the earth to Mars in a spaceship moving with a constant velocity. Neglect all other objects in the sky. Which part of the figure best represents the weight (net gravitational force) of the passenger as a function of time ?

1. A                             
2. B
3. C                             
4. D

What is the intensity of gravitational field of the centre of a spherical shell?

1.     $Gm/r^2$           

2.    g

3.      Zero             

4.    None of these