Q.What is geostationary satellite?

A geostationary satellite orbits in the equatorial plane with a 24-hour period matching Earth's own rotation, so it stays fixed above the same point on the ground.

Step 1: Define the key requirement.

For a satellite to appear "stationary" to an observer standing on Earth, its angular velocity of revolution around the Earth must exactly match the Earth's own angular velocity of rotation about its axis.

Step 2: State the conditions this imposes.

This requires three things simultaneously:

1. The orbital period T must equal Earth's rotation period, T = 24 hours (more precisely, one sidereal day ≈ 23 h 56 min).
2. The orbit must be circular.
3. The orbit must lie in the equatorial plane (0° inclination), and the satellite must move in the same direction as Earth's rotation (west to east).

Step 3: Find the orbital radius (from Kepler's third law / the centripetal-gravity balance).

Using GMm/r^2 = m(4π^2/T^2)r with T = 24 h gives an orbital radius of about 42,164 km from Earth's centre (≈ 35,786 km above the surface).

Step 4: State the definition. …