Friday puzzle -- a boat in a pool

Wabash or Adderley?

The effect would be different - unless Adderley had his sax with him at the time.

Making a splash

I can't think of a clever way to say it....so if need be I'll spend the rest of the morning where they keep the head lights in a submarine.

If I remember my classes in stability and bouyancy correctly, other than making a splash as cannon ball enters the water and some ripples for a while, the net balance of forces and the water level remain unchanged. The boat would ride slightly higher in the water.

Lee

Re: Friday puzzle -- a boat in a pool

The cannonball would rapidly sink and hit the pool floor causing a small crack. The pool water would seep out and the pool would be completely empty in a month.

T.

:-)

:-(

Originality points

Nothing--I Think

A body displaces it own weight in water. It was part of the weight of the boat. But if it is on the bottom does it weigh anything?

Re: Nothing--I Think

I think the water level would go down and here is my reasoning. While the cannonball is in the boat it causes the displacement of the entire boat to be more raising the water level. Once the cannonball is tossed out of the boat it is only displacing the size of the cannonball so the water level will go down.

Answer

Kudos to Bill for the rapid solution and creative obfscation, and to Jim for the clear explanation. A FLOATING object will displace water with the same mass as its mass. But an object not supported by the water will displace water only equal to its volume.

Another way to look at this is to imagine lowering the cannonball down by rope. Let's say it weighs 80lbs. The cannonball is contributing 80 pounds to the mass of the boat, that must be counteracted by displaced water. After you lower it into the water, its pull on the rope is reduced to 70 pounds (using 8 as the specific gravity of iron). The "cannonball-boat system" still has the same mass that must be supported by displaced water. The cannonball is displacing 10 pounds of water, and contributing 70 lbs to the mass that must be supported by the water displaced by the boat, so the water level doesn't change. However, when the cannonball reaches the bottom of the pool and the rope goes slack, the cannonball still displaces 10 pounds of water, but the boat floats 70 pounds higher (80 pounds higher than before the cannonball was lowered into the water), lowering the water level.

Re: Answer

Stayed out of this one because I knew the answer. A long time ago in a galaxy far, far, away, I posted a variation of this puzzle here on the trivia board.

Oh, well

Very few truly original puzzles, I guess. Hopefully that doesn't happen too often. It will be note future, not subjunctive tense) embarrassing when I repost one that I have already posted.

Re: Oh, well

Not a problem. It was a long time ago. I am fairly sure that I have reposted at least one or so or variations of them over time.