Does it weigh less to transport flying birds?
Question
I look forward to the podcast each week. It took me quite a while to catch up to the present shows as I've listened to all of them to date. I hope the show runs as long as you folks want it to.
My question actually comes from a cartoon panel in a 1940 New Yorker magazine:
If I have a small truck with 500 lbs of birds in the cargo area, and 1/2 of them are in flight at any one momemt, will the weight be less?
Mike Zinner
Minneapolis, Minnesota (yes it's getting quite cold already) USA
Answer
We answered this with regards transporting birds in aeroplanes...
Dave - Not for very long. Basically, birds hold themselves up by pushing air downwards and so, as they push air downwards, they get an equal opposite reaction, they're held upwards. The problem is that the air is going to keep on moving downwards until it hits something else. If it were in a plane, it will hit the bottom of the plane and therefore, that air will get slowed down and it'll transfer exactly the same force to the plane. So for the time it takes for the movement of air to get from the bird to the plane, the plane will weigh less but as soon the air hits the plane, then it will go back to what it weighed before.
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