Tensions of cable over a pulley

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    Cable Pulley
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Discussion Overview

The discussion revolves around the tension in a string connected to pulleys in a mechanical system. Participants explore whether the tension remains constant along the string under various assumptions about the system's ideal conditions, including frictionless pulleys and massless strings. The context includes theoretical considerations of mechanics and equilibrium.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • One participant questions whether the tension in the string will be the same, suggesting that the presence of concentrated loads from the pulleys may affect this.
  • Another participant argues that if the pulleys are ideal and the string is massless, the tension should be the same throughout the string, as any difference would imply acceleration at some point in the string.
  • A third participant challenges the initial assumptions by stating that without a load in the diagram, there is no force to create tension, implying that the system must be in equilibrium for the tension to be uniform.

Areas of Agreement / Disagreement

Participants express differing views on the conditions under which tension in the string can be considered uniform. There is no consensus on whether the assumptions of ideal conditions are sufficient to conclude that tension is the same throughout the string.

Contextual Notes

The discussion highlights the importance of assumptions regarding the ideal nature of the pulleys and string, as well as the need for a load to create tension in the system. The implications of equilibrium are also noted but remain unresolved.

aerograce
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In the figure attached, we have one section which has three bars all pin-connected together and pin fixed on the ground. We have two pulleys connected with the section by string. And we have one string starting from the left fixed pin to the right fixed pin. I am thinking whether the tension along the string will be same or not. I am imagining that, it is a single string with two concentrated loads(Excerted by pulley), so it is not the same. can you help me justify that
 
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No figure is attached to your post.
 
SteamKing said:
No figure is attached to your post.
Here it goes:)
 

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aerograce said:
I am thinking whether the tension along the string will be same or not. I am imagining that, it is a single string with two concentrated loads(Exerted by pulley), so it is not the same.

If the pulleys are ideal frictionless pulleys and the string is an ideal massless string, then the tension in the string will be the same everywhere. If it weren't, then some point in the string would experience a greater pull from one side than the other and would be accelerating - and that's not happening.
 
@aerograce.
Your diagram has nothing in it to cause a force - if we are assuming that everything is 'ideal'(massless and frictionless). You would really need to put a load somewhere and then you could calculate the forces on the pulley supports, for instance, and the tension all along the string could be assumed to be the same.
We are assuming that the system is in equilibrium??
 

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