open university for norwegian blues
The total amount of matter (ie. mass) present in the a/c remains constant, ignoring fuel burn... (imagine it as a glider). However the instant the birds are airborne then there is no longer a direct reaction between the a/c and birds.... therefore although the total mass remains constant within the a/c, the load experienced by the a/c reduces.
Think of the birds as balloons resting on the perches which are then inflated with hot air so they rise and hover. The perches no longer have to support the balloons as the balloons have become "weightless" in the atmosphere of the a/c. Therefore the weight of the birds / balloons is no longer experienced by the a/c.
Consider yourself standing on the ground, you are supported by the earths crust. Then you jump into the air and the earths crust ceases to support your weight, although the total mass of the system (you + earth) remains constant.
... confused..? so are all the parrots!!
- If the mountain appears too high... then try approaching from a differrent side!