Q.

A remote-sensing satellite of earth revolves in a circular orbit at a height of 0.25×106 m above the surface of earth. If earth’s radius is 6.38×106 m and g=9.8ms-2, then the orbital speed of the satellite is:                [2015]
 

1 9.13 km s-1  
2 6.67 km s-1  
3 7.76 km s-1  
4 8.56 km s-1  

Ans.

(3)

The orbital speed of the satellite is, v0=Rg(R+h)

where R is the earth’s radius, g is the acceleration due to gravity on earth’s surface, and h is the height above the surface of Earth.

Here, R=6.38×106m,  g=9.8ms-2,  h=0.25×106m

   v0=(6.38×106m)(9.8ms-2)(6.38×106m+0.25×106m)

              =7.76×103ms-1=7.76km s-1