The right prop can pull your presentation skyward

When people talk about props, they usually say something like John Zimmer did in an article at Presentation Guru on April 25, 2017 titled How to “prop up” your next presentation:

“The word ‘prop’ comes from the term ‘theatrical property’. If you watch a play, props are objects used by actors on stage to add realism to the story and to help advance the narrative.”

But prop also is short for propeller - a device used to propel a vehicle such as the Spitfire airplane (shown above). A prop can simplify describing an object by modeling one feature in a situation – shown either much smaller or larger than in reality.

For example, one danger during landing an aircraft is a ground loop - catching a wing tip on the ground, and then having a rapid rotation causing damage as described above in a YouTube video.

A balsa wood toy airplane small enough to be held in one hand can be used to demonstrate a ground loop, by using the other hand to represent the wing tip hitting the runway or grass.

About fifteen years ago I gave a speech to insurance claims adjusters about lamp analysis after vehicle accidents. As shown above, a halogen headlamp is only about 4- 1/2 inches tall and the filament is about 1/4 inch long. Tail lamps and their filaments are even smaller.

I used a plastic Slinky Jr. toy, as shown above, for a greatly enlarged model of a filament. I held an end in each hand and then moved my hands rapidly upwards and then stopped to ‘twang’ it like the string from a guitar.

The filament is a coil of tungsten wire. When electrical current is applied, it is heated to a temperature of above 4000 F and it glows. In air, a filament would react with oxygen and burn out in seconds. It is surrounded by a quartz or special glass bulb filled with an inert gas plus a small amount of a halogen (iodine or bromine).      

Many vehicle accident will deform or break the filament even if the bulb remains intact. Careful examination of the filament with an optical microscope will often determine its condition at impact. Tungsten is hard and brittle when cold, but soft and ductile when hot, The type of deformation the filament displays shows whether it was cold (off) or hot (on) at the time of impact. A clean break of the filament means it probably was cold at impact. A deformed filament with looping or twisting of the wire means it probably was hot at impact. But if the impact was not severe enough either to deform or break the filament in an intact bulb, then it is not possible to determine whether it was on or off.  

When the bulb is broken, two additional microscopic observations can be made. First, if the bulb was on, then the air that enters causes the filament to burn up and produce tungsten trioxide, a yellowish powder. Second, the operating temperature for a filament is above the melting point for a bulb, so there may be melted particles attached to the filament.

Images of Spitfire propeller and an H4 headlamp came from Wikimedia Commons.