Tension and Spring Forces

[ritwik06]

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?

[Topher925]

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]

http://img401.imageshack.us/img401/9550/diag1kw3.jpg (http://imageshack.us)
http://img401.imageshack.us/img401/9550/diag1kw3.ab9c003442.jpg (http://g.imageshack.us/g.php?h=401&i=diag1kw3.jpg)

[ritwik06]

http://img401.imageshack.us/img401/9550/diag1kw3.jpg (http://imageshack.us)
http://img401.imageshack.us/img401/9550/diag1kw3.ab9c003442.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?

[tiny-tim]

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:

[ritwik06]

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:

[tiny-tim]

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)