Dot Physics

There is this show “Weapon Masters” – I think it comes on the discovery channel. It is not a bad show. The basic idea is that they have this history guy talk about the historical aspect of some type of weapon and this other guy tries to make an improved version. Last night the goal was to recreate the original flame thrower mounted on a boat.

They found a boat and they needed to test it’s sea worthiness. The builder guy (sorry, I don’t know his name) estimated that they would have 1000 lbs of equipment in the boat. To simulate this weight, they put 4 guys and two barrels of water in the boat and motored around.

After a little bit, the history guy noticed one of the barrels was leaking water. *”Quick! Put your finger in the hole before we all sink!”* he said. This is where he doesn’t understand floating. I think I can explain his error with two simple pictures:

![Screenshot 05](http://scienceblogs.com/dotphysics/wp-content/uploads/2008/10/screenshot-051.jpg)

The first picture has the boat with the water in the barrel. The second picture has some water that has leaked out. Either way, the total mass of water in the boat is the same. If you would like to talk more about floating, [here is my post about MythBuster's lead ballon](http://scienceblogs.com/dotphysics/2008/09/mythbusters-how-small-could-a-lead-balloon-be/) – same idea.

I think the weapon master history guy should have said:

*”Quick! Plug the hole before my shoes get wet! But, we won’t sink because the mass of water is the same no matter if it is in the barrel or in the boat.”*

Comments

  1. #1 Diversity
    October 13, 2008

    Everybody knows water is heavier when it is flatter. That is why there is capillary rise, raindrops high in the sky are round, high altitude lakes are precipitously deep, and oceans – defining the geoid – are flat at their tops.

    Make a solid ball of clay. Place it on a hard surface. Pound on it. The more you make it heavier the flatter it gets. A sufficienctly large gravitational field would also flatten it – by having it collapse flat under its own weight. See? Flatter is heavier. Pancakes are flat, loaf bread is chunky. Which weighs more? Chairs are light, tables are heavy. A door hinged upright moves with a fingertip. Try opening a flat door to a root cellar.

    A mercury barometer has its narrow mercury thread spontaneously rise a full 76 centimeters straight up. You don’t see the barometer’s flat pool of mercury rising, do you? The only difference is the shape. Flatter is heavier.

  2. #2 Fran
    October 13, 2008

    Hah! I love Diversity’s comment! Hilarious!

  3. #3 Tim Makepeace
    October 27, 2008

    I would like to respond to the post about the water in the flame thrower boat that was being tested for the show Weapon Masters. As someone who was actually in the boat at the time, (I am the builder guy) I agree with all of the issues brought up by both posts. I do understand the physics principle of the same combined load on the boat whether the water is in the barrel in the boat or just in the boat, but more important to me at the time was keeping my shoes dry. This was even more ridiculous because as soon as we got out of the boat the skies opened up and it rained about 2 inches in the ten minutes it took to get the boat out of the water and on to the trailer. But even more concerning at the time of our great voyage, than my shoes getting wet, was my worry about the increased weight in the boat caused by the increased flatness of the water. The poster “Diversity” has it exactly right, the water in the boat was in a transformative state going from a tall configuration i.e. water in a tall barrel/light, to a flat configuration i.e. flooded boat/heavy. It was hard to tell at the time whether the boat was sinking or the river was rising. The river, being flat, was being hit by rain drops– tall in proportion, so clearly the river was becoming taller thus lighter and therefore rising and the boat was becoming flatter and heavier.
    “Diversity’s” theory is confirmed, Flatter is heavier.
    If you want to see some production stills from the Flame Thrower episode aka “Greek Fire” go to my web site: http://www.tmakepeace.com/%22Weapon_Masters%22/%22Weapon_Masters%22.html
    – Tim Makepeace

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