Moving a mass through water

  1. I am planning building a sub. I am tring to find the amount of energy it takes to move it.
    I think it should be equal to the energy needed to move the same volume of water.

    For example say the sub had the volume of 10,000 cubis feet.

    1. Is my assumptin right?

    2. what formulas are ther for this?

    3. Is more energy needed at deeper depth? Why?

    If You have Ideas post thanks
     
  2. jcsd
  3. PhysicoRaj

    PhysicoRaj 437
    Gold Member

    Welcome to PF.

    1.) No. Consider a case where you move a ball through air. Does it take the same energy it takes to move the same volume of air? No! The same way, the work to be done depends on it's mass and how far you want to move it.Work. But the force applied depends on the friction of the medium. Since viscosity of water is more than that of air, more force is needed. The viscous drag increases with velocity so more the speed, more force to apply. Ultimately the increased force means increased work to be done.

    2.) work done=force applied*distance travelled. And the force applied includes the force you need to overcome the viscous drag.Work

    3.)You will also have to consider one more important factor, http://en.wikipedia.org/wiki/Buoyancy

    And these might help you:Archimedes principle applied to subs

    Principle of operation of sub
     
    Last edited: Apr 17, 2014
  4. Chronos

    Chronos 9,973
    Science Advisor
    Gold Member

    Think of the case of an airplane. Aerodynamic principles must be taken into account to optimize design.
     
  5. russ_watters

    Staff: Mentor

    Homeade subs are extremely dangerous and a great way to die. Do you intend this to be flooded (and you wear scuba gear) or filled with air for you to breathe?
     
  6. PhysicoRaj

    PhysicoRaj 437
    Gold Member

    OMG :bugeye: I thought about somthn like this

    [​IMG]
     
  7. Bobbywhy

    Bobbywhy 1,908
    Gold Member

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