What is meant by the phrase "a consistent method of measurement"?

Where is the potential energy throughout the loading, cocking, and releasing of the trebuchet?

The earth exerts a gravitational force of 500 n on amy. what is amy’s mass in kg?

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.