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Deceleration in water

  1. Apr 5, 2015 #1
    So this is about a modelling project i'm doing.

    If you have an object that was being towed in water and the towing force is suddenly removed. There is a force F=1/2(density of fluid)(C constant)(A)V^2 that acts on the object. I am trying to find the distance X it will take for the object to come to rest. If its initial velocity V is known. Say V is 3.5 m/s.
  2. jcsd
  3. Apr 5, 2015 #2


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    hi there

    I would imagine the shape of the object, how deep it sits in the water, smoothness of its surface
    would also have significant effects on how far it would travel ... maybe other factors as well

    consider the difference between the bow ( pointy end) of a boat and the stern, the flat end
    and the effect that would have

  4. Apr 6, 2015 #3
    Hello dave,

    I am allowed to make assumptions obviously. The object is rectangular in nature. My issue is that the water resistance force is variable as it is dependent on the velocity of the object and the object is decelerating. So how could one find the distance X the object travels before it comes to rest is my question.
  5. Apr 6, 2015 #4


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    I think first you need to know how drag depends on velocity. If it was being towed at constant speed then the tension in the towing rope will be equal to drag at that velocity. So thats one point on the curve. Another is the origin. Finally you need to know if it's proportional to velocity, velocity2, or velocity3 etc
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