What is the least speed with which a body must be thrown up from the Earth’s surface so that it escapes the Earth’s gravity and never returns (ignore air resistance)?
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → About 11.2 km/s
This least speed is the escape speed, \(v_e=\sqrt{2gR}\). With \(g=9.8\) m/s\(^2\) and \(R=6.4\times10^{6}\) m it is about 11.2 km/s; about 7.9 km/s is the speed of a satellite orbiting just above the Earth’s surface.