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  1. keannu's Avatar
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    #1

    surface drag

    Is this drag made by the rope or the natural one of the water? It's confusing. If it is the water one, how is it related to pulled rope? I'm all confused.

    ex)Some scientists measured the drag that a seal must overcome in swimming. To do it, first they trained seals to chomp down on a rubber mouthpiece that could be pulled by a rope. Then they measured the pounds of force on the rope when the seals were towed at a different speeds both at the surface and sumberged in a swimmming pool. As expected, the faster the seal was moving, the greater the drag force that worked against that movement. At a higher speed of four miles an hour the surface drag was almost three times greater than the submerged drag. But even at the seal's low cruising speed of three miles per hour, drag at the surface was almost two times greater than the drag when submerged. The researchers concluded that swimming below the surface must be a lot easier.

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    #2

    Re: surface drag

    Quote Originally Posted by keannu View Post
    Is this drag made by the rope or the natural one of the water? It's confusing. If it is the water one, how is it related to pulled rope? I'm all confused
    Not the rope -- the rope is simply connecting between the seal and the force measuring deivce (scale). The various swimming positions of the seal and the speeds were used to calculate the drag force of the seal. Did the rope add to the drag? Perhaps but since the surface area of the rope is so much smaller than the seal it was most likely ignored or a minor adjustment made.

    Not a teacher - AmE native

  2. keannu's Avatar
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    #3

    Re: surface drag

    Quote Originally Posted by allenman View Post
    Not the rope -- the rope is simply connecting between the seal and the force measuring deivce (scale). The various swimming positions of the seal and the speeds were used to calculate the drag force of the seal. Did the rope add to the drag? Perhaps but since the surface area of the rope is so much smaller than the seal it was most likely ignored or a minor adjustment made.

    Not a teacher - AmE native
    Is the drag the resistant force of the water or the seal? That's what I'm curious about..

  3. 5jj's Avatar
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    #4

    Re: surface drag

    The drag is the force the water (or whatever something is moving through) that acts against that movement.

  4. keannu's Avatar
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    #5

    Re: surface drag

    Quote Originally Posted by fivejedjon View Post
    The drag is the force the water (or whatever something is moving through) that acts against that movement.
    I thought the seal and the rope were going in opposite directions, but now I see carefully, the seal was just pulled by the rope so that the resistance(drag) could be measured. Right? I'm sorry to bother you.

  5. 5jj's Avatar
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    #6

    Re: surface drag

    The boat is pulling the rope, which is pulling the seal, They are all going in the same direction. Assuming that the drag on the rope is negligible, then the drag recorded on the measuring device would be the drag on the seal

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