Besides earning money why do people work​

Two technicians are discussing the common u-joint. technician a says its input and output speeds should be equal. technician b says that it normally has two yokes. which technician is correct?

The most common battery cable terminal is a that provides a large surface contact area with the ability to tighten the terminal onto the battery post using a nut and bolt.

Why were most movies from the late 1890s until the early 1930s only filmed in black and white? there were only a few people who could afford the technology to produce color motion pictures back then. audiences did not want color motion pictures until later. the film used to make color motion pictures often overheated, which was a safety hazard, so it was generally not allowed. color films had to be hand-colored, frame by frame.