I keep getting “Escape velocity” questions wrong in Gravitation. What's the trap?
confusing it with orbital velocity.
The usual trap: confusing it with orbital velocity. How to avoid it: escape velocity is √2 times the orbital velocity at the surface. Go back to the definition — the minimum speed to leave a planet's gravity, v = √(2GM/R) ≈ 11.2 km/s for Earth.
Key point
Escape velocity
Common mistake
confusing it with orbital velocity.
Memory tip
escape velocity is √2 times the orbital velocity at the surface.
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