The orbital speed for an earth satellite near the surface of the earth `7km-s^-1` ,. If the radius of the orbit is 4 times the radius of the earth is the orbital speed would be

Options

A. ` 3.5 km-s^-1`
B. `7km-s^-1`
C. `7sqrt2 km-s^-1`
D. ` 14 km-s^-1`

Answer

D

Explanation

Orbital speed in an ornit is `V_0 = sqrt(gR)`
R= 4R
Rightarrow `V_0 = sqrtg(4R) = 2 sqrtgR` ,
therefore `V_0= 2xx7 = 14kms_1`