Question Details

Given radius of earth ‘R’ and length of a day ‘T’ the height of a geostationary satellite is [G – Gravitational constant, M – Mass of earth]

Options

A

(4π²GM/T²)⁰.³³

B

(4πGM/R²)⁰.³³ - R

C

(GMT²/4π²)⁰.³³ - R

D

(GMT²/4π²)⁰.³³ + R

Correct Answer :

(GMT²/4π²)⁰.³³ - R

Solution :

The correct option is (GMT²/4π²)⁰.³³ - R.

To find the height of a geostationary satellite, we need to balance the gravitational force acting on the satellite with the centripetal force required to keep it in a circular orbit around the Earth.

Let:
- M be the mass of the Earth.
- R be the radius of the Earth.
- h be the height of the geostationary satellite above the Earth's surface.
- r be the orbital radius of the satellite from the center of the Earth, such that:
r=R+h
- m be the mass of the satellite.
- T be the time period of the satellite's rotation, which is equal to the length of a day (since it is a geostationary satellite).

The gravitational force between the Earth and the satellite is given by Newton's law of gravitation:
Fg=GMmr2

The centripetal force required to keep the satellite in orbit is:
Fc=mω2r

Here, the angular velocity ω is related to the time period T by the relation:
ω=2πT

Equating the gravitational force to the centripetal force:
GMmr2=m(2πT)2r

Canceling the mass of the satellite m from both sides and simplifying:
GMr2=4π2T2r

Rearranging the equation to solve for the orbital radius r:
r3=GMT24π2

Taking the cube root of both sides (which is equivalent to raising to the power of 1/3, or approximately 0.33):
r=(GMT24π2)0.33

Since the height of the satellite above the surface is h=r-R, we substitute the expression for r:
h=(GMT24π2)0.33-R

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