Unequal tension of a rope in a pulley system

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Discussion Overview

The discussion revolves around the concept of unequal tension in a rope within a pulley system, exploring the conditions that lead to this phenomenon. Participants are examining theoretical aspects of tension in relation to acceleration, mass differences, and the mechanics of pulleys.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • Some participants inquire about the conditions that lead to unequal tension in a rope, particularly in scenarios involving acceleration and mass differences.
  • One participant suggests that tension may vary along the length of the rope and seeks clarification on how pulleys affect this tension.
  • Another participant explains that when two different masses are attached to the ends of a rope in a pulley system with mass, the tension must be unequal to exert a tangential force on the pulley, which is necessary for its acceleration.
  • A further elaboration indicates that to achieve rotational acceleration of the pulley, a net moment must be applied, necessitating different tensions on either side of the rope.

Areas of Agreement / Disagreement

Participants express similar concerns regarding the conditions for unequal tension, but there is no consensus on the specific mechanics or implications of these conditions. Multiple viewpoints on the role of mass and acceleration in determining tension remain present.

Contextual Notes

Discussion includes assumptions about the system's dynamics, such as the effects of mass on tension and the role of acceleration, which are not fully resolved. The relationship between tension and the rotational dynamics of the pulley is also a point of exploration.

tchentroll
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I am having a bit of difficulty with the concept of unequal tension in a rope. What are the conditions for unequal tension? I read that the tension is the same when there is no acceleration. Why is this the case? Can someone explain this concept to me? Thanks :)
 
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tchentroll said:
I am having a bit of difficulty with the concept of unequal tension in a rope. What are the conditions for unequal tension? I read that the tension is the same when there is no acceleration. Why is this the case? Can someone explain this concept to me? Thanks :)
Maybe you can explain to us first about what you mean by "unequal tension." Are you referring to tension variations along the length of the rope? And where does the pulley come in?

Chet
 
For example if two different masses are attached to the ends of a rope and the rope is part of a pulley system that has mass, why is the tension in the rope unequal on both sides?
 
tchentroll said:
For example if two different masses are attached to the ends of a rope and the rope is part of a pulley system that has mass, why is the tension in the rope unequal on both sides?
To accelerate the massive pulley, the rope must exert a tangential force on it, and the pulley will exert an equal but opposite tangential force on the rope. To balance that force on a piece of rope, the tensions at both ends of that piece must be different.
 
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tchentroll said:
For example if two different masses are attached to the ends of a rope and the rope is part of a pulley system that has mass, why is the tension in the rope unequal on both sides?
To get the pulley to accelerate (rotationally), you need to apply a net moment to the pulley. So the part of the rope attached to one of the masses must have a higher tension in it than the part of the rope attached to the other mass. This will translate into a net moment about the axis of the pulley. If the tensions were the same, there would be no net moment, and the pulley would not rotate.

Chet
 
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