Slipgate's post got me thinking...

cbxjeff

Consider a 40' enclosed & sealed semi trailer. If it houses 400 sparrows, does it weigh more if they are flying or resting? This was asked me when in '62 I interviewed for my first real job at the Union Carbide research lab in indy.

dan kelly

i`ll bite..common sense says that it would weigh more if they were airborne rather than resting,but i suppose if they were flying the air pressure from them flapping their wings would affect the weight? i`m sure theres a trick there somewhere.

matwor

The downpressure created from their flapping their wings is directly proportional to the weight of the bird, thus creating the same downforce on the floor of the semi trailer as if they were standing on the floor as opposed to being in flight. Therefore we can deduce the semi trailer to weigh the same regardless the birds are in flight or non-flight.

Marc1301

I would have to say it weighs more if they are resting as they become part of the structure per se.

When flying they are not connected to the structure, and are simply disturbing some air.

Like Dan,......I am sure there is a trick waiting!

givette

No. Force on the floor caused by little sparrow feet, or force on the floor caused by wings pushing the air downward is the same. Remember: we're talking about hovering birds. Different with birds in a climb (or in a descent). It's all about vector analysis. Trig function. Best, Joe

barto

Mythbusters busted this on a couple years ago.
No difference in weight.
[^]barto[^]

KSUmarksman

Its an enclosed system, the balance of forces remains the same unless you add external forces (like a crane [:)])

cbxjeff

I was told by the guy that decided to hire me that the weight is the same if the birds are flying or at rest on the floor. He claimed that there would be a slight weight shift when the birds were rising from the floor or decending back to it.