Question

A mountaineer is doing a vertical rappel. She is using a big boulder/stone as her anchor. The Mountain guides association advises that in this type of situation, the boulder should be bigger than a refrigerator. The boulder should be sitting on a surface that is horizontal rather than sloping. The aim for this problem is to approximate the coefficient of static friction between the boulder and the ledge is required if this setup is to hold the climber's body weight. For reference, granite blocks typically has a static coefficient of approximately 0.6. It is expected that our calculation will result in a value that's smaller than this. There is no friction where the rope goes over the lip of the cliff.

What is the minimum value of the static friction coefficient, express in terms of m-mass of the climber, V -volume of the boulder, d- density, and g