Which factor determines orbital velocity?

Which factor determines orbital velocity?

• A. The spacecraft's color
• B. The radius of the orbit and the planet's gravity
• C. The pilot's experience
• D. The altitude above the atmosphere only

Answer: (B)

Orbital velocity is set by how strong the planet’s gravity is and how far you are from the planet’s center. For a circular orbit, gravity pulls inward just enough to keep you on a curved path, and your tangential speed must satisfy v = sqrt(GM/r), where M is the planet’s mass (gravity) and r is the distance from the planet’s center (the orbit’s radius). So a larger orbit radius means you need a slower speed, while a stronger gravitational pull means you need a faster speed. The color of the spacecraft, the pilot’s experience, or altitude above the atmosphere by itself doesn’t determine the orbital speed—altitude affects r and, through that, the required speed, but the speed is fundamentally set by gravity and radius.

Orbital velocity is set by how strong the planet’s gravity is and how far you are from the planet’s center. For a circular orbit, gravity pulls inward just enough to keep you on a curved path, and your tangential speed must satisfy v = sqrt(GM/r), where M is the planet’s mass (gravity) and r is the distance from the planet’s center (the orbit’s radius). So a larger orbit radius means you need a slower speed, while a stronger gravitational pull means you need a faster speed. The color of the spacecraft, the pilot’s experience, or altitude above the atmosphere by itself doesn’t determine the orbital speed—altitude affects r and, through that, the required speed, but the speed is fundamentally set by gravity and radius.