A box-shaped metal can has dimensions 6 in by 2 in by 12 in high. All of the air inside the can is removed with a vacuum pump. Assuming normal atmospheric pressure outside the can.

a. Find the total force on one of the 6 in by 12 in sides.
b. Find the gauge pressure at the bottom of a swimming pool that is 17 feet deep.

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.