2008-10-16

a 4-bladed fan has an rpm of 65. if you are watching tv what sort of shadow will you expect the tv to cast on the ceiling by way of the moving fan?

if the fan moves faster than the blink of the light source (eg fluorescent/tv @60hz) it will appear at an earlier spot, which repeated would look like a shadow rotating opposite its caster, slower or backwards. (see also: timing gun for automotives)

if a 4-blade fan moves at 60 rpm in a room with one pulsed light source (a tv conveniently outputing at 60hz), how many orbital shadow derivatives could you calculate, and what would be their values?

@ 60 rpm = primary blade
@120 rpm = primary and tertiary
@240 rpm = primary, secondary, tertiary, and quaternary sectors complete rotation



2008-10-16