A rope hanging over edge of table.

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The problem involves calculating the fraction of a rope that can hang over a table's edge without slipping, given a static friction coefficient of 0.3. To solve it, one must equate the frictional force acting on the rope on the table to the gravitational force acting on the hanging portion. The frictional force is determined by the weight of the rope on the table, while the gravitational force depends on the length of the rope hanging off the edge. It is emphasized that the mass or length of the rope is not necessary for the solution, as only the gravitational force and the coefficient of friction are relevant. A diagram illustrating the forces can aid in understanding the problem better.
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The coefficient of statis friction between a rope and the table on which it rests is 0.3. Find the fraction of the rope that can hang over the edge of the table before it begins to slip.

This is an extra credit problem so we haven't learned this yet. I don't know where to start but I'm guessing that to find that fraction of the rope, you need the mass,the weight and the gravitational force and stuff??
cluless >.< please help.
 
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Rope hanging over edge of table.

question
The coefficient of static friction between a rope and the table on which it rests is 0.3. Find the fraction of the rope that can hang over the edge of the table before it begins to slip.

Equation/ attempt at solution
well, i googled this question and the equation i came up with was
(0.3)(M-n[M/L])g=[n M/L]g .

But as this is an extra credit problem and we haven't learned this yet, I am not sure what I'm doing.
Clueless, please please help.
 


Draw a diagram of the forces.
You have a weight pulling down on the hanging part, how will this weight depend on the length?
This is balanced by the friction on the table part, friction = 0.3 * downward force (ie the weight of the part still on the table)

If you think carefully the actual weight/metre of the rope doesn't matter, can you see why
 
you don't need to now the length or mass of the rope to solve this. Only gravity and the coefficient of friction are needed.
To solve you need to set the force of friction equal to the force of gravity.
Keep in mind only the portion of the rope on the table will contribute to the force of friction and only the part off of the table will contribute to the force of gravity.
 
Moderator's note: two threads merged into one.

Note to myaaxcore: please do not start multiple threads to ask the same question.
 

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