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So there's this set of scales right?

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  • So there's this set of scales right?

    The plane question got us all thinking so I've gone looking for more.

    Two identical containers have the same volume of water, and one is placed on each pan of a double-pan balance. Obtain a hollow plastic ball and a steel ball that have the same volume. A string from the ceiling suspends the steel ball so it is completely submerged in the water on the left pan. The hollow ball is held submerged in the water of the right pan by a string fastened to the bottom of the beaker. Now what will be the condition of the double pan balance?

    1. The balance indicator will read zero. The scale is balanced.
    2. The left pan (with the steel ball) moves down.
    3. The left pan rises.
    Discuss.

  • #2
    Balance.
    In complete darkness we are all the same. It is only our knowledge and wisdom that seperate us. Dont let your eyes deceive you.
    Its the little things that make the difference
    Originally posted by IPIT on relationships
    If either/both of you can take a dump with the other person being next to you within a week of meeting them then you're in with a VERY good chance.

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    • #3
      +1 balance (in the real world)
      Originally posted by zobo
      I'd be more prolific in answering but I thought of a use for the othe

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      • #4
        now lets say that over time the right side wall fall due to the weight of the string..... but then hang on.... would the weight of the string be able to overcome the friction of the water attempting to push past the steel ball in the water on the left? Oh my what a conundrum.
        In complete darkness we are all the same. It is only our knowledge and wisdom that seperate us. Dont let your eyes deceive you.
        Its the little things that make the difference
        Originally posted by IPIT on relationships
        If either/both of you can take a dump with the other person being next to you within a week of meeting them then you're in with a VERY good chance.

        Comment


        • #5
          Originally posted by Aphex View Post
          would the weight of the string be able to overcome the friction of the water attempting to push past the steel ball in the water on the left?

          Yes. But the upward force of the ball trying to float on the water would counteract the weight of the string, so the water friction would win and the scales stay still.
          Originally posted by zobo
          I'd be more prolific in answering but I thought of a use for the othe

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          • #6
            It will tip towards the side with the plastic ball, if the weight of the plastic is not negligible.
            this is because both sides have ~the same relative density, however, the weight of the plastic sphere is acting through the base of the container
            Last edited by Kryzaach; 08-12-2007, 02:33 PM.
            "In all the human societies we have ever reviewed, in every age and in every state, there has seldom if ever been a shortage of eager young males prepared to kill and die to preserve the security, comfort and prejudices of their elders, and what you call heroism is just an expression of this fact; there is never a scarcity of idiots." -The Culture

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            • #7
              Only if the scales are sensitive enough to react to the presence of the string and the ball, which they won't if you've got a significant amount of water (or to be more accurate if the ratio of the mass of the water to the combined mass of the ball and string is large).
              Originally posted by zobo
              I'd be more prolific in answering but I thought of a use for the othe

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              • #8
                so we are assuming the mass of the plastic ball filled with air, + all string involved is negligible?
                "In all the human societies we have ever reviewed, in every age and in every state, there has seldom if ever been a shortage of eager young males prepared to kill and die to preserve the security, comfort and prejudices of their elders, and what you call heroism is just an expression of this fact; there is never a scarcity of idiots." -The Culture

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                • #9
                  assume it's a real world problem

                  super sensitive scales

                  air filled ball

                  take everything into account

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                  • #10
                    I'm confused. Where's the fucking treadmill?
                    It is worth remembering that when a person dies, his or her funeral contributes to the Gross Domestic Product, even though they are no longer there.
                    - David James

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                    • #11
                      Originally posted by Kryzaach View Post
                      so we are assuming the mass of the plastic ball filled with air, + all string involved is negligible?

                      i was, yes. Otherwise, you're right. Of course. ^_^
                      Originally posted by zobo
                      I'd be more prolific in answering but I thought of a use for the othe

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                      • #12
                        I had to draw a diagram to come up with an answer.



                        I think there will be balance. The forces of the ball all cancel out, no net force. Only forces that aren't being cancelled out by another force is the weight force of the water, but in the nature of the balance these cancel eachother out.
                        sigpic

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                        • #13
                          Originally posted by Jedi View Post
                          I had to draw a diagram to come up with an answer.



                          What the [email protected]#K?

                          i think that confuses people more then it helps
                          ellE

                          jenius

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                          • #14
                            sooooo.... whats the answer?

                            any utube vids for this one? lol
                            Hello, you've reached the psychiatric hotline. If you are obsessive/compulsive, press 1 repeatedly. If you have multiple personalities, press 2, 3, 4, and 5. If you are simply paranoid, just stay on the line - we know who you are.

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                            • #15
                              I rekn the left pan rises coz of the weight of the hollow ball. I mean, the steel ball's weight is irrelevant coz it's hanging from the ceiling right?

                              -s-

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