Explained: Beaker Ball Balance Problem
This is the solution to: http://youtu.be/QD3hbVG1yxM Watch this first!
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You have made your prediction and now it is time to see what happens when I release thebalance. Ready? In three, two, one. The balance tips towards the right, towards the hanging,heavier ball. But why does this happen?Well, the best way I can think of to explain this is that both balls displace the sameamount of water. So they both experience the same upward buoyant force which is equal tothe weight of the water they displace. That is just Archimedes Principle. But by Newton’sThird Law, that means there must be equal and opposite forces down on the water in bothbeakers. So you would think that both beakers would get heavier by this same amount.Now for the hanging ball the beaker does get heavier by this amount, because the buoyantforce is now supporting some of the weight that used to be supported by this tensionin the string. But it is now reduced and so beaker actually has more weight....
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You have made your prediction and now it is time to see what happens when I release thebalance. Ready? In three, two, one. The balance tips towards the right, towards the hanging,heavier ball. But why does this happen?Well, the best way I can think of to explain this is that both balls displace the sameamount of water. So they both experience the same upward buoyant force which is equal tothe weight of the water they displace. That is just Archimedes Principle. But by Newton’sThird Law, that means there must be equal and opposite forces down on the water in bothbeakers. So you would think that both beakers would get heavier by this same amount.Now for the hanging ball the beaker does get heavier by this amount, because the buoyantforce is now supporting some of the weight that used to be supported by this tensionin the string. But it is now reduced and so beaker actually has more weight....
