Gravity /electromagnetism /measuring

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had a thought experiment like this , a lorry is on a weighbridge inside is a 100kg weight surrounded above and below by 2 perfectly calibrated electromagnets, when the the magnets are switched on the weight is suspended in mid air ,does the lorry weigh 100kg less and does the above magnet need slightly more power than the one below assuming both are pulling toward ? hope this isn't too stupid!
 
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The lorry weighs the same.
 
what about if the lorry is full of seagulls and one moment they are all at rest then on the weighbridge they all hover in midair , same weight ?
 
Yes, of course. Btw, Mythbusters did an excellent show on that myth, confirming the physics.
 

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Thread 'Dirac's integral for the energy-momentum of the gravitational field'

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