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

[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://g.imageshack.us/g.php?h=401&i=diag1kw3.jpg

 

[ritwik06]

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?

 

[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!

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

 

[ritwik06]

Hi ritwik06!

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

I wish to know their direction dear Tim.

 

[tiny-tim]

… ah!

I wish to know their direction dear Tim.

ah … the tension acts in both directions.

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

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

(same with compression)