How is the tension equal in both sides of the string

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  • Thread starter Thread starter Miraj Kayastha
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    String Tension
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Discussion Overview

The discussion revolves around the concept of tension in a string over a pulley with two different masses attached to its sides. Participants explore the conditions under which tension can be considered equal on both sides of the string, addressing theoretical implications and assumptions related to mass, acceleration, and the nature of the pulley.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions how tension can be equal on both sides of the string when different masses are involved.
  • Another participant suggests that the smaller mass accelerates upward, implying a need for more force than just its weight, while the greater mass accelerates downward, requiring less force in the rope than its weight.
  • A participant seeks clarification on the statement regarding the opposing forces on either side of the pulley.
  • It is proposed that if the pulley is massless and frictionless, the forces must be equal because there can be no extra force on either side of the string length.
  • One participant introduces an analogy involving rockets pulling on a string to illustrate that tension remains the same in either direction along an ideal string, regardless of the presence of a pulley.
  • Several participants express a desire to understand whether the conditions discussed are assumptions or established principles.

Areas of Agreement / Disagreement

Participants express differing views on the nature of tension in the system, with some agreeing on the conditions under which tension can be considered equal, while others question whether these conditions are assumptions or facts. The discussion remains unresolved regarding the implications of different masses on tension.

Contextual Notes

Participants reference assumptions about the pulley being massless and frictionless, which may not hold in all scenarios. The discussion does not resolve whether these assumptions are universally applicable or if they introduce limitations to the analysis.

Miraj Kayastha
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How is the tension equal in both sides of the string, if the string is over a pulley with two different masses attached to its sides?
 
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The smaller mass accelerates up, which requires more force than the just the weight. On the other side its the opposite.
 
Can you explain what you mean by "On the other side its the opposite."
 
The greater mass accelerates down, which requires less force in the rope than the weight.
 
Miraj Kayastha said:
How is the tension equal in both sides of the string, if the string is over a pulley with two different masses attached to its sides?

The same force acts on both masses but they are not in equilibrium so there is acceleration. If the pulley is massless and frictionless, there can be no extra force on one side or the other of the string length - so the forces must be equal. The force on the pulley will be less than the sum of the weights because the CM of the two masses is accelerating downwards.
 
I did not get you, can you explain in a different way please
 
How's this?
If there were two rockets, pulling at either end of a string then would not the tension be the same in either direction and all along the ideal string? (That's the basis for all the Mechanics we ever use.)
Merely putting a pulley in the way and re-directing the forces, there is nothing to change that. The force on the pulley will be twice the tension because the pulley is not accelerating and must be in equilibrium.
 
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i want to know whether it is an assumption or not
 
sumanprakasam said:
i want to know whether it is an assumption or not
The assumption is:
sophiecentaur said:
If the pulley is massless and frictionless, there can be no extra force on one side or the other of the string length - so the forces must be equal.
 

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