Weight of 1 kg becomes 1/6 kg on moon. If radius of moon is $1.768\times {10}^{6}m$, then the mass of moon will be -

1. $1.99\times {10}^{30}kg$                        
2. $7.56\times {10}^{22}kg$
3. $5.98\times {10}^{24}kg$                       
4. $7.65\times {10}^{22}kg$

Let g be the acceleration due to gravity at earth's surface and K be the rotational kinetic energy of the earth. Suppose the earth's radius decreases by 2% keeping all other quantities same, then

1.  g decreases by 2% and K decreases by 4%

2.  g decreases by 4% and K increases by 2%

3.  g increases by 4% and K increases by 4%

4.  g decreases by 4% and K increases by 4%

The distance between centre of the earth and moon is 384000 km. If the mass of the earth is $6\times {10}^{24} kg$ and $G=6.66\times {10}^{-11} N{m}^2/k{g}^2$ . The speed of the moon is nearly -

1. 1 km/sec                         
2. 4 km/sec
3. 8 km/sec                         
4. 11.2 km/sec

A body is projected vertically upwards from the surface of a planet of radius \(R\) with a velocity equal to half the escape velocity for that planet. The maximum height attained by the body is:
1. \(\frac{R}{3}\)
2. \(\frac{R}{2}\)
3. \(\frac{R}{4}\)
4. \(\frac{R}{5}\)

A satellite is launched into a circular orbit of radius \(R\) around the Earth while a second satellite is launched into an orbit of radius \(1.02~\text{R}\). The percentage difference in the time periods of the two satellites is: 

Distance of geostationary satellite from the center of the Earth $(R_e=6400 km)$ in terms of $R_e$ is-

1. $13.76 R_e$                        

2. $10.76 R_e$

3. $6.59 R_e$                            

4. $2.56 R_e$

Energy required to move a body of mass m from an orbit of radius 2R to 3R is

1.    $GMm/12R^2$               

2.    $GMm/3R^2$

3.     $GMm/8R$                 

4.     $GMm/6R$

If the radius of the earth contracts by 2% and its mass remains the same, then weight of the body at the earth surface :

1.  Will decrease                      

2.  Will increase

3.  Will remain the same             

4.  None of these

The kinetic energy needed to project a body of mass m from the earth surface (radius R) to infinity is -

1.   mgR/2                 

2.  2 mgR

3.   mgR                   

4.   mgR/4

A satellite is to revolve round the earth in a circle of radius 8000 km. The speed at which this satellite be projected into an orbit, will be 
1. $3 km/s$                     

2. 16 km/s

3. 7.15 km/s                   

4. 8 km/s