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Force applied? I think

  1. Feb 3, 2015 #1
    I am going to try and explain this as best I can. I have a drum submerged in water (200ltr drum) filled with +- 150ltr of air. This is attached to a chain that goes around a sprocket at the bottom of the tank and the sprocket is mounted to a shaft that goes out of my tank. How do I calculate what Kilo Newton or Kilo Watt will be applied to the shaft when I release the drum to go to the surface. I know that the uplift would basically be 150kg that pulls on the chain.

    Thanks Rainier
  2. jcsd
  3. Feb 3, 2015 #2

    Andrew Mason

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    Welcome to PF Rainerc!

    Hint: the upward force is related to the weight of the water that is displaced by the drum. What is the downward force? What is the NET upward force? (I think you can neglect the weight of the air in drum to keep it simple).

    PS. if your question is how to convert the gravitational force on a kg into Newtons, multiply by 9.8 (N/kg force)

    Last edited: Feb 3, 2015
  4. Feb 3, 2015 #3


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    If you want to calculate the Power (kW) involved then you need to know something of the distance actually moved upwards and the time taken. (Time taken would be hard to work out but Energy / Work could be fairly straightforward to calculate - given the height the drum rises.

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