Solving Equilibrium in Friction: Find d for Mass m

[wayneo]

Hi, please anyone help me to answer this question

A mass m,is attached to 2 equal peices of string each of length, whose ends are attached to rings around a rod. If the static coefficient of friction between the rings and the rod is u, find the largest distance d between the rings such that the mass is at equilibrium.

 

[Hootenanny]

Can you show some of your working / thoughts?

 

[wayneo]

Ive got the answer as d= 2uL/square root of (1 + u squared) but I am a bit stuck with the working out

 

[Hootenanny]

Have you drawn a diagram showing all the forces acting?

 

[wayneo]

no but there arent any forces given as it is in equilibrium

 

[wayneo]

nemore ideas?

 

[wayneo]

any1 ?

 

[wayneo]

hard huh ?

 

[Hootenanny]

There are forces but they are all balanced. Try calculating the tension in the strings, then resolving the tension horizontally parallel to the rod.

 

[sporkstorms]

no but there arent any forces given as it is in equilibrium

I think what you're trying to say is that there is no net force. There are, most certainly, forces acting in the system.

Listen to Hootenanny, s/he speaks words of wisdom.

Your goal is to find out where those rings will be when the net force is zero. In order to do so, you really need to make a diagram.

 

[Hootenanny]

Listen to Hootenanny, s/he speaks words of wisdom.

Thank-you sporkstorms