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Interview Question

Interview Cupertino, CA

If you and a large brick are in a boat floating in a pool

  , will the water level rise or fall when the brick is tossed into the water? What if the brick is a large piece of Styrofoam and thrown into the water?

Interview Answer

4 Answers


cannot believe Apple ask this kind of middle school physics question... The water level will not change.

Anonymous on Aug 2, 2011

Your answer indicated the necessity of this question.

Anonymous #2 on Oct 2, 2011

If the brick was the size of a pebble but very dense, the water level would rise since the pebble displaces minimal water compared to the boat. On the other hand, if the brick was large (perhaps even larger than the boat), less dense, and of the same weight as the pebble, the water level would rise.

Anonymous on Oct 16, 2011

The water level will decrease ( if the brick has a density greater than water, which of course a conventional brick does). When in the boat, the brick will displace a mass of water equal to it's own. So if it has a mass of 1kg it will displace 1kg of water. When thrown overboard it will now displace an amount of water equal to it's volume. As it sinks, it's density must be grater than water and therefore it's 1kg mass will take up a smaller volume than 1kg of water. Therefore the water level will decrease. As a styrofoam brick has a lower density than water it will not sink when thrown overboard. When floating it will displace a mass of water equal to that of the brick and therefore the water level will remain the unchanged.

Clueless bob on Jun 2, 2012

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