As Promised, the Physics of Typewriters

First seen as a relatively mature product in the 1910s, the typewriter quickly became an indispensable part of the 'modern' office and home.

An entirely mechanical, analogue device, the typewriter uses a complex series of metal levers to raise 'typebars' (longer levers with characters on the ends). These typebars strike an ink ribbon and press it against the page. This impulse transfers some of the ink from the ribbon onto the page. At the end of a line of text, a typist must press the carriage return; a bar which moves the paper over and up to prepare for the next line to be entered.

A truly classic example of mechanical advantage, typewriter keys only need to be depressed half an inch or so to cause one of the type bars to swing up many inches and strike the ink ribbon and paper. This conversion lessens the force the type bars can exert at the end of their radius, but means this point moves very quickly. Because momentum is equal to mass multiplied by velocity, the end of the typebar builds up a great deal of momentum. This momentum is then used as an impulse to compress the paper and ribbon against the character and actually 'type' something.