Modeling Deceleration of Object Towed in Water

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Discussion Overview

The discussion revolves around modeling the deceleration of an object being towed in water after the towing force is removed. Participants explore the factors affecting the distance the object will travel before coming to rest, considering aspects of fluid dynamics and drag forces.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant presents a formula for drag force acting on the object, which is dependent on fluid density, drag coefficient, cross-sectional area, and velocity.
  • Another participant suggests that the shape of the object, its depth in the water, and surface smoothness significantly influence the distance traveled after the towing force is removed.
  • A participant notes that the object is rectangular and raises the challenge of calculating the distance traveled due to the variable nature of water resistance as the object decelerates.
  • One participant emphasizes the need to understand how drag varies with velocity, mentioning the importance of knowing whether drag is proportional to velocity, velocity squared, or velocity cubed.

Areas of Agreement / Disagreement

Participants express various viewpoints on the factors affecting the deceleration and distance traveled, indicating that multiple competing views remain without a consensus on the modeling approach.

Contextual Notes

Participants acknowledge the need for assumptions in their modeling, particularly regarding the nature of drag force and its dependence on velocity, which remains unresolved.

marawan
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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.
 
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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

Dave
 
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.
 
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 that's 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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