This month's Challenge Question: Specs & Techs from GlobalSpec:
A tall 0.5 kg glass filled with 1 L water is placed on a
balance to be weighed; the glass has a 0.25 kg metal object hanging from its
outside edge. The object is then moved inside the glass (making sure it
doesn't touch the bottom), and the weight taken again. Does the weight
change? Does the pressure on the bottom of the glass change?
And the answer is:
The
weight does not change because all the original weight (object) is weighted
by the balance. The pressure at the bottom of the glass certainly changes because the pressure is only a function of the height of water inside the
glass. The metallic object does not add to the pressure because it is not
touching the bottom, but by inserting the metallic object inside the glass, it
displaces water. The height of the water inside the glass is higher so the
pressure increases.
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