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Throwing A Pineapple Through A Floor

  1. May 22, 2007 #1
    So I want to prove my friend wrong when he says he can throw a pineapple through our living room floor and I don't really know how I would calculate that.

    I've determined our floor is composed of different layers, looking something like this:

    ------ Parquet flooring [~1 cm] (800 kg/m3)
    ------ Plywood [~1.3 cm] (700kg/m3)
    --|--- Insulation [~15.2 cm] (500kg/m3)
    ------ Drywall [~0.6 cm] (800kg/m3)

    I figure the variables needed to figure this out would be the distance the pineapple would have to go through (the thickness of each layer), the density of each layer, the mass of the pineapple (about 1 kg), and how much force a male can possible throw a pineapple with so I can compare.

    I'm going to assume he won't hit any pipes or wires and that the pineapple won't smash and crack open by pressure just to simplify the question.

    I know what information I have, and I know what I'm looking for (force)...I just don't know how to get there. It's been too long since I've taken a physics class. I think I would have to do a seperate calculation for each layer. I think it has something to do with the force exerted by the layer being greater then the force exerted by the pineapple so the pineapple would go through it and it has a positive net force.

    I need help though. I'm stuck! I don't know any equations that would help me figure this out. I just know using common sense, it won't work lol. :shy:
  2. jcsd
  3. May 22, 2007 #2


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    Think about this! Could you throw a dense ball of rigid, dense material (a steel ball) through a floor? Perhaps if you could move the floor out to an open area and throw the ball down from a tremendous height. Otherwise, no. So how could someone throw an equally massive, but larger, softer, more deformable lump of stuff at your floor and make it penetrate? You can ask for numerical proof, but perhaps you should take it upon yourself to calculate the penetrating power of a Nolan Ryan fastball, and see what is reasonable.
  4. May 22, 2007 #3
    I already know he can't do it. I have suggested that he just try it but he's so sure that he can, he doesnt want to put a hole in my floor.
  5. May 22, 2007 #4


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    Get him a piece of plywood and have at it.
  6. May 22, 2007 #5


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    Are you sure this isn't a trick? What exactly does he mean by throwing it "through" a floor? Maybe think outside the box?
  7. May 23, 2007 #6


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    You can do one layer at a time as a plate bending problem with the edges constrained and a force at the center. However, I think Russ has the best idea. Get a piece of 1/2" plywood and have him throw it through that first. It aint gonna happen.
  8. May 23, 2007 #7
    I smell a trick, Holly. No way can somebody throw a pineapple through your living room floor. Maybe it's just a play on words. Or maybe, maybe it'll be a really ripe pineapple. Splat! All over that parquet. Then he grins and says "Oh I guess I couldn't" before running off leaving you to clear up the mess. Pineapples are mildly acidic so maybe it would leave a stain, I'm not sure.
  9. May 23, 2007 #8


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    Maybe he's not thinking classically, but quantum mechanically.
  10. May 23, 2007 #9


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    "Pineapple" was World War II slang for "hand grenade". See also the James Bond novels, and some video games.

    Though somebody got their fruit mixed up, because "grenade" comes from the French and Spanish words for "pomegranate".
  11. May 23, 2007 #10
    I appreciate the responses! I don't think he's trying to trick me. He's also my room mate so any mess made he'd be responsible for cleaning up. He honestly believes he can do it. I'm not sure what logic he's using but he's totally serious nonetheless.

    So the equation to calculate penetrating power of a bullet is W x V / 450240?
    That's in really stupid units though like grains and feet per second. Is there another one that I'm missing with easier metric units?

    If I figure out the penetrating power of the pineapple, how do I find out how much is necessary to break through the floor? Something to do with density and thickness I'm assuming?
  12. May 23, 2007 #11
    Maybe somebody else can answer that, holly, I can't.

    Just a thought: maybe he intends to drill a hole in the floor first. Not that he'd go through with it. But if there's already a hole somewhere, he might intend to use it. If for example there's a soil pipe running down the wall from a bathroom upstairs, all he'd have to do is chop the pineapple up and throw it down the toilet.
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