Troy.........
Hoist by your own petard!
Yes, w = mg.
The problem mentioned 'weight' and 'physics'.
Weight is not the same as Mass; as you rightly say it is related to 'g'. Earth's gravity varies with the distance from the centre of the earth.
If the birds are flying above their perches they will weigh less, below and they will weigh more, and all over the place - a bit of averaging will be required....constantly!
We all 'weigh' less at the top of Mount Everest.
So the mass of the aeroplane will remain constant, but not the weight.
However, the difference in weight will be very tiny. (Half a feather??).
A bit of a trick question.
Well, that's my two penny worth!
Last edited by Gerund; 10th September 2002 at 04:38.