Can someone help with this question? Explain why the angular momentum of the Moon is conserved, even though the gravitational force
of the Earth exerts a net force (a centripetal force directed toward the Earth) on the Moon.

Engines for propeller-driven aircraft are limited in their maximum rotational speed by the fact that the tip speed of the propeller must not approach the speed of sound in air (mach i). taking 6 ft as a typical diameter for a propeller of a light airplane and 1100 fils as the speed of sound, find the upper limit on the rpm (revolutions per minute) of the propeller shaft.