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Does getting sucked up require more energy then getting pushed away?

  1. Jun 3, 2014 #1
    For instance The object has same mass in both cases.
    And the force of getting sucked and pushed away is also the same.

    Does getting sucked up require more energy then getting pushed away?
     
  2. jcsd
  3. Jun 3, 2014 #2

    ZapperZ

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    Why don't you test this with an idealized adiabatic piston and an ideal gas trapped inside the piston? Is the work done in compressing the piston by an amount equal or different than the work done by the gas in expanding back to the piston's original position?

    Zz.
     
  4. Jun 3, 2014 #3
    I don't have one.
     
  5. Jun 3, 2014 #4

    ZapperZ

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    No one has an "idealized piston". It wasn't meant to be an experiment. It was meant for you to calculate!

    Zz.
     
  6. Jun 3, 2014 #5

    Nugatory

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    The required energy will depend on the efficiency of the device doing the sucking/pulling; if they were perfectly efficient there would be no difference. In practical applications pushing is often more efficient, but this is by no means universally true.
     
  7. Jun 3, 2014 #6

    sophiecentaur

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    No one has asked you the actual context of this question. A sketch of the sort of arrangement you are considering would help. I have a feeling you may not be talking in terms of pistons and cylinders.
     
  8. Jun 5, 2014 #7
    If "sucking up" you mean in the vertical direction upwards; and by being pushing away you could mean in any direction; then there would be a difference.

    By going upwards, the mass will have an increase in gravitational potential energy. You will have to supply this energy.
    By pushing away, say in the horizontal direction, the gravitational potential energy stays the same. If on a surface, friction due to sliding will require an energy expenditure.

    Pushing away in any other direction from the horizontal entails a change in potential energy. This could help you in if the final position is below the initial, or add to the energy expenditure if above the initial position.

    You may have to clarify your question.
     
  9. Jun 6, 2014 #8

    sophiecentaur

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    One thing that's certain, in open conditions, is that 'blow' can be directed from a jet, producing a higher pressure in a given direction. If you have a low pressure in an orifice, air will flow in from all directions and you can't 'focus the suck' as much because, for a given total amount of air flow, the pressure gradient is less.
     
  10. Jun 6, 2014 #9
    NEWTON's third LAW can work here.
    Besides, Question is not complete.
     
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