Question

What is the escape speed from the Moon?

The Moon’s mass is 7.4×10^22 kg and its radius is 1700 km.

The speed of a spacecraft moving in a circular orbit just above the lunar surface: v = 1700 m/s

Express your answer using two significant figures.

v = __________ m/s

Answer 1

1/2 m v^2 - G M m / R escape velocity equal to energy at surface

v^2 = 2 G M / R = 2 * 6.67E-11 * 7.4E22 / 1.7E6

v^2 = 2 * 6.67 * 7.4 / 1.7 * 105 = 5.81E6

v = 2410 m/s = 2400 m/s