Object w/ Constant Speed Doesn't Lose KE Faced w/ Resistance

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Discussion Overview

The discussion revolves around the behavior of an object moving at a constant speed in the presence of resistance, particularly in the context of fluid dynamics and energy conservation. Participants explore concepts such as kinetic energy, potential energy, hydrostatic pressure, and the Bernoulli effect, seeking to understand how these factors interact when fluid flows through a narrowing airway.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant states that when air travels through an airway at a constant flow rate, total energy decreases due to friction converting energy into heat, leading to a decrease in potential energy.
  • Another participant argues that the moving object does not lose kinetic energy because of the conservation of mass, suggesting that the fluid must speed up as it moves through a narrower section.
  • A participant expresses confusion about hydrostatic pressure and its relationship to kinetic energy and fluid velocity, questioning how velocity can increase with increased resistance.
  • Another participant clarifies that most fluids are incompressible, implying that the density remains constant and that fluid must flow faster through a narrower exit to maintain mass conservation.

Areas of Agreement / Disagreement

Participants express differing levels of understanding regarding the concepts discussed, particularly around hydrostatic pressure and the implications of fluid dynamics. There is no consensus on the relationship between kinetic energy and resistance in this context, as some participants challenge the initial assumptions while others provide explanations.

Contextual Notes

Participants mention concepts such as the Bernoulli effect and conservation of mass without fully resolving the implications of these principles in the context of the discussion. The relationship between pressure types and fluid velocity remains unclear for some participants.

sameeralord
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Hello,

"Potential Energy (PE) + Kinetic Energy (KE) = Total Energy

When air travels through an airway at a CONSTANT FLOW RATE, the total energy of the fluid (PE + KE) decreases because friction converts some of this energy into heat. Since the fluid is moving at a constant flow rate, the loss is in potential energy (decrease in hydrostatic pressure)."

I don't understand this. Shouldn't the moving object lose K.E. Shouldn't resistance decrease speed.
 
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Hello sameeralord! :smile:
sameeralord said:
… Shouldn't the moving object lose K.E. Shouldn't resistance decrease speed.

Nope …

conservation of mass! :wink:​
 


Thanks for the help but I still don't get it. I think the reason for that is I don't understand what is hydrostatic pressure, I researched but I don't get it.

"As we move down the airway, the tubes begin to narrow. When a tube narrows, fluid velocity increases causing an increase in KE at the expense of PE (ie. a compensatory decrease in hydrostatic pressure). This is referred to as the BERNOULLI EFFECT."

How does the fluid velocity increase when the resistance also increases when the tube narrows. Is the pressure inside this tube, exerted by moving molecules (KE) or hydrostatic pressure. I don't get it.
 
Hi sameeralord! :wink:

Forget pressure …

most fluids are incompressible, meaning that their density is constant.

So the amount of fluid going into a particular volume equals the amount going out …

if the exit is narrower than the entrance, then the fluid must be going faster!

That's all it is! :smile:​
 

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