**Example:**The orbital speed for an Earth satellite near the surface of the Earth

is 7 km/sec. If the radius of the orbit is 4 times the radius of the Earth, what would be the orbital speed?

**Solution:**Orbital speed is $v=rGM_{e} $ for a satellite at a distance $r$ from the Earth's centre.

Firstly, the satellite is said to be near the earth's surface, we take the radius as Earth's radius, '$R$'.

$⇒v=RGM_{e} =7km/s$

Now, the radius of the orbit is 4 times the radius of the earth$(R)$, the orbital speed $(v_{_{′}})$ is given by,

$v_{_{′}}=4RGM_{e} =4 1 RGM_{e} =0.5×7=3.5$ km/s