🚀 go-pugleaf

>>  If one has a half-ton pickup, and a box containing one ton of
>> birds was placed in the bed of the truck, the load would be too heavy
>> for the truck to move.  But what would happen if the box was beaten
>> with a stick, causing at least half of the birds to start to fly inside
>> the box, since the pickup can haul one half of a ton.  Would the truck
>> be able too move?  Would the same result occur if the situation was
>> identical, but took place in an airplane?
>>
>I presume the airplane is totally enclosed so whatever lift the birds get is
>at the expense of downward air pressure, so the weight is the same.  But if
>the truckload of birds is open to the outside some proportion (not 100% surely)
>of that downward force of air will be against the ground rather than the truck,
>so I'd say more than half of the birds would have to fly.
>
>---

Does that mean that you also would have different pressures being measured
at the bottom of a cylindrical container of liquid compared to a vertical
funnel or any other shaped vessel.  Surely not?  The lift for each bird
must come from somewhere and the somewhere eventually has to be the bed of
the truck.

Now if you want to measure the pressure between the tyres and the ground
and want to question whether the birds are accelerating upwards or not then
that becomes more interesting.

How about the egg timer (the old type with genuine sand running through a
glass hourglass)  Does it weigh more or less, or even no change at all,
when the container is inverted and the sands commence to run out ?

Try it with your most accurate balance and observe but only after you have
written down your guestimate and reason/explanation and handed it to an
impartial observer !

Ain't Physics fun ?
David Bailey                              !  Faculty of Science &
Technology,
University of Western Sydney, Nepean            !  P.O. Box 10, KINGSWOOD  2747
Phone (047) 360 429  Fax (047) 360 713    !  Australia