How Do Tension and Spring Forces Work in Different Parts of a String?

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Homework Help Overview

The discussion revolves around understanding the forces acting on a string or spring, particularly tension, in response to an applied force. The original poster expresses confusion regarding the direction and magnitude of tension at various points along the string when a force is applied at one end.

Discussion Character

  • Exploratory, Assumption checking

Approaches and Questions Raised

  • Participants explore the concept of tension in a massless string, questioning its direction and magnitude at different points. The original poster attempts to determine the tension at points A, B, and C, while others provide insights into the nature of tension as a force that acts in opposing directions.

Discussion Status

There is an ongoing exploration of the topic, with some participants providing guidance on the uniformity of tension in a massless string. Multiple interpretations of the forces involved are being discussed, particularly regarding the direction of tension.

Contextual Notes

Participants note that the string is assumed to be massless, which influences the discussion on tension. There is also mention of the need for clarity on the direction of forces acting on the string.

ritwik06
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I am a bit confused about such forces that act in a string or a spring. I am unable to guess their direction.
Therefor I prepared myslf some examples through which i can understan the concpt of these forces.

In diag1
A force F is applied at end C. What will b the tensions at points A,B(mid point),C. Find their directions and their magnitues. (if the string has no mass)

I can guess about tension at point A. Its going to pull the block of mass m. Therefore, tension will act away in the rightward direction. Am I right? What about the other points?
 

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Your attachment doesn't seem to be working. You shouldn't have to guess what direction the opposing force will be applied, it should be easy to realize. A spring will always want to return to its original position.

The equation for this force is: F = -k*dx
 
ritwik06 said:
http://img401.imageshack.us/img401/9550/diag1kw3.jpg
http://g.imageshack.us/g.php?h=401&i=diag1kw3.jpg

A force F is applied at end C. What will b the tensions at points A,B(mid point),C. Find their directions and their magnitues. (if the string has no mass)

I can guess about tension at point A. Its going to pull the block of mass m. Therefore, tension will act away in the rightward direction. Am I right? What about the other points?
 
Last edited by a moderator:
ritwik06 said:
A force F is applied at end C. What will b the tensions at points A,B(mid point),C. Find their directions and their magnitues. (if the string has no mass)

I can guess about tension at point A. Its going to pull the block of mass m. Therefore, tension will act away in the rightward direction. Am I right? What about the other points?

Hi ritwik06! :smile:

A massless string (all strings in exam questions are massless :wink:) has the same tension all the way along. :smile:
 
tiny-tim said:
Hi ritwik06! :smile:

A massless string (all strings in exam questions are massless :wink:) has the same tension all the way along. :smile:

I wish to know their direction dear Tim. :smile:
 
… ah!

ritwik06 said:
I wish to know their direction dear Tim. :smile:

ah … the tension acts in both directions.

Tension is a pair of opposing forces on each tiny little bit of the string. :smile:

(And if the string is massless, the two opposing forces are equal.)

(same with compression)
 

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