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Plankton Sampling Procedure

  1. Apr 7, 2014 #1
    1. The problem statement, all variables and given/known data

    I have a boat moving at 2.3 mph towing a plankton net in water weighting 8.5lbs. I want the net to be towed at a depth of 10m from the surface. How much rope do I need to let out from the boat?

    2. Relevant equations
    basic trig sin=cos=tan

    3. The attempt at a solution
    I cannot find the angle of the rope in the water from the surface of the water.
    Last edited: Apr 7, 2014
  2. jcsd
  3. Apr 7, 2014 #2


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    In general the answer will depend on the actual dynamics of the net and water. How many simplifying assumptions are we allowed to make?

    The net has some weight so there's a force going down, it might have some buoyancy so there could be a (smaller) force pointing up, there's the tension in the rope pointing towards the boat, and there might be drag forces due to the water (let's not talk about turbulence!) pointing backwards away from the direction of motion. Which, if any, of these are we allowed to neglect?
  4. Apr 8, 2014 #3
    Thanks for the response. Basically in a perfect world you could use all the parameters to calculate this but for the matter of getting an estimate I think we could neglect the turbulence and maybe tension. I'm am by now means a physics major but this problem is going to be used in current sampling techniques.
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