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Birds in a covered lorry?
If a lorry were carrying a load of birds and they all started flying around inside the freight area, would the weight of the lorry decrease? If not why?
Sounds a stupid question but we were discussing it at work and I'd like to be able to tell them the physics answer.
xaipete!
So does the 'thrust' exist indefinitely until the door is opened?
1 Answer
- oldprofLv 71 decade agoFavorite Answer
Actually the Myth Busters did this one on telly. There was no difference in weight.
The rationale for the no difference answers was that the birds had to thrust equal to their own individual weights to lift off the bed of the lorry. And that thrust displaced the individual weights on a one for one basis. That is, there was no net change because the lost weight of the birds was replaced by the sum of the thrusts that kept them airborne.
It was further suggested on Myth Busters that, had the bird been left to fly off and away, there would have been a commensurate drop in weight because the thrusts would have been removed as well.