Physics

Physics

Problem

Two identical satellites, P and Q, orbit the same planet in circular paths of radii rr and 2r2r, respectively. a. (i) Explain qualitatively how the orbital speed of a satellite depends on the radius of its orbit around a given planet. b. (ii) Without using actual numbers, determine which satellite has greater kinetic energy and by what factor. c. (iii) Discuss how the orbital period of Q compares with that of P and justify your answer using appropriate mathematical reasoning.
Intuitive explanation

The key to comparing these orbits is Kepler's third law, which links orbital radius to orbital period. Since both satellites orbit the same planet, you can set up a ratio of their periods without needing to know the planet's mass. The satellite closer to the planet moves faster and completes its orbit in less time—use the r3/2r^{3/2} relationship to find how their periods compare, then derive any other orbital quantities (speed, energy) from that fundamental connection.

Intuitive explanation

The key to comparing these orbits is Kepler's third law, which links orbital radius to orbital period. Since both satellites orbit the same planet, you can set up a ratio of their periods without needing to know the planet's mass. The satellite closer to the planet moves faster and completes its orbit in less time—use the r3/2r^{3/2} relationship to find how their periods compare, then derive any other orbital quantities (speed, energy) from that fundamental connection.

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