Ian Stirling wrote:

Jim Rusling wrote:
Ian Stirling wrote:

Jim Rusling wrote:
"MLD" wrote:

snip
2. Small boat in a pond. In the boat is a boy and a large cinder block. The
boy throws the cinder block overboard and it promptly sinks to the bottom.
Does the level of the pond rise or fall after the block is thrown overboard?
Obviously, assuming that the change in water level could be measured or
observed.

The pond level will actually fall a little. While the block is in the
boat it is displacing its weight in water. Once it is in the water it
is displacing its volume of water.

Are insulating aerated blocks ever called cinder blocks?
Might any have a density under 1?

Then it would not sink to the bottom.

And the level of the lake would remain unchanged.

If the block floated, then you are right the lake level would be
unchanged. The question stated that the block sank to the bottom of
the lake.

--
Jim Rusling
Partially Retired
Mustang, OK
http://www.rusling.org