“does a slightly deflated ball weigh less than an inflated one?”
Of course. Everybody knows the truck driver carrying 11 tons of canaries in hid trailer can safely get over the 10 ton limit bridge by banging on the sides of the trailer to put them all in flight.
Hey! That’s MY joke! I told a variation of that joke at an auction the very first time I auctioneered in public in 1968.