On Sat, 20 Dec 2003 03:28:16 -0800, Ken Cutt wrote:
Ok I am confused by all these wanna be wet blocks . A block in water
will displace its volume regardless of its mass . But in the boat it
displaces its equal mass of water . Which is greater .

Actually, in the boat it displaces its *weight*, not mass, but otherwise
correct.

So hanging off a
rope attached to a boat displacing already its volume but pulling down
on the boat additionally displacing its mass ?

It displaces its volume, which applies some bouyant force to the
block. This offsets some of its *weight* (not the same thing as mass),
so its full weight isn't pulling down on the boat. The net result is that
there's no change in the total amount of water displaced, regardless
of whether the block is in the boat or suspended in the water below it.

So what is the point of
all this ?

The point is that it isn't intuitively obvious what will happen in these
situations. You have to be able to think rationally about the physics
to get the right answer. So it is really a test of your knowledge of
physics, and your ability to think rationally.

Now, with the knowledge gained from this thought experiment, here's
another brain teaser. Which weighs more (at the Earth's surface, in
air), a metric ton mass of feathers, or a metric ton mass of lead?
Think carefully.

Gary