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Pressure problem

  1. Aug 15, 2005 #1
    (a) A very powerful vacuum cleaner has a hose 2.86cm in diameter. With no nozzle on the hose, what is the weight of the heaviest brick it can lift? (b) A very powerful octopus uses one sucker, of diameter 2.86cm, on each side of a shell of a clam in an attempt to pull the shells apart. Find the greatest force the octopus can exert in salt water 32.3m deep.

    (a) - I'm not sure how I know the power of the vacuum, but I think I'm suppose to use [tex]P = P_0 + pgh[/tex] although I'm not sure how.

    (b) I have no clue how to do this :-\

    Could anyone lend a hand?
     
  2. jcsd
  3. Aug 15, 2005 #2
    For the first part you need to know what pressure the vacuum cleaner is generating.

    Once you have this you need to think about over what area this pressure is acting.

    Remember

    Pressure * Area = Force

    And the force relates to the weight.

    The second part is not so different... :smile:
     
  4. Aug 15, 2005 #3
    Well, the problem doesn't give me the pressure of the vacuum. Is that something I can assume?
     
  5. Aug 15, 2005 #4

    HallsofIvy

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    Staff Emeritus
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    Of course, a vacuum cleaner doesn't actually pull anything- it reduces the density of air in it and then the pressure of the outside air pushes things in.
    The minimum possible density is, of course, 0 which would result in the air pressure (one atomosphere) pushing against the brick. Multiply standard one atmospher air pressure by the area of the hose to find the maximum possible force.
     
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