One end of a 30-m rope is tied to a tree; the other end is tied to a car stuck in the mud. the motorist pulls sideways on the midpoint of the rope, displacing it a distance of 2 m. if he exerts a force of 80 n under these conditions, determine the force exerted on the car.

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.