Escape velocity
The minimum speed an object needs to escape from the gravitational field of a massive body to infinity. Escape velocity v_e = √(2GM/r) where M is the body's mass and r is the distance from its centre.
Formula
v_e = √(2GM/r)
Real World
SpaceX's Falcon 9 must accelerate its second stage to roughly 11.2 km/s to send payloads beyond Earth's gravity entirely; falling short means the payload remains in orbit rather than escaping.
Exam Focus
Show that escape velocity is independent of object mass by cancelling m in the KE = GPE derivation — examiners award a method mark for this.
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