CCEA A-Level Physics 1210
Physical Quantities, Scalars and Vectors
Moments and Equilibrium
Linear Motion and Dynamics
Newton's Laws of Motion
Linear Momentum and Impulse
Work, Energy and Power
Current, Charge and Potential Difference
Resistance and Resistivity
Internal Resistance and Potential Dividers
Waves
Refraction
Lenses
Superposition, Interference and Diffraction
Quantum Physics
Wave-Particle Duality
Astronomy
Practical Skills and Data Analysis
Deformation of Solids
Thermal Physics
Uniform Circular Motion
Simple Harmonic Motion
The Nucleus and Radioactive Decay
Nuclear Energy, Fission and Fusion
Gravitational Fields
Electric Fields
Capacitors
Magnetic Fields
Charged Particles and Accelerators
Gravitational Fields
Geostationary satellites
- 3 things to know
- Unit A2 2
Overview
Geostationary satellite, three conditions a geostationary orbit must satisfy and one disadvantage of a geostationary orbit for communications.
What you need to know
Answer each one before you reveal it.
State the three conditions a geostationary orbit must satisfy.
Why must a geostationary satellite orbit from west to east?
Questions from this subtopic
Each one with the model answer underneath.
- 1
What is a geostationary satellite?
Model answer
A satellite that stays above the same point on the Earth's equator, appearing stationary to an observer on the ground.
- 2
State the three conditions a geostationary orbit must satisfy.
Model answer
The period must equal the Earth's rotation period of 24 hours, the orbit must lie in the plane of the equator, and the satellite must travel in the same direction as the Earth's rotation, from west to east.
- 3
Why must the period be exactly 24 hours?
Model answer
Only then does the satellite complete one orbit in the time the Earth takes to turn once, so it stays above the same point.
- 4
Why must a geostationary orbit lie over the equator?
Model answer
An orbit in any other plane would carry the satellite north and south of the equator during each revolution, so it would not stay above one point.
- 5
Why must the satellite orbit from west to east?
Model answer
The Earth rotates from west to east, so a satellite going the other way would move across the sky rather than keeping pace with the ground.
- 6
Calculate the radius of a geostationary orbit, taking the Earth's mass as 6.0 × 10²⁴ kg and the period as 8.64 × 10⁴ s.
Model answer
r³ = GMT²/(4π²) = 4.00 × 10¹⁴ × 7.46 × 10⁹ ÷ 39.48 = 7.56 × 10²², so r is the cube root of that, 4.2 × 10⁷ m.
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