# Lifting a prism; coefficient of friction

1. May 29, 2012

### kate12

1. The problem statement, all variables and given/known data
A prism has a mass of m = 80 g, and you wish to lift it, touching
the upper two faces only. If the coecient of friction between the prism’s surface and
your skin is  = 0:4, what is the minimum force that must be applied to each face?

2. Relevant equations
F=μR

3. The attempt at a solution
I drew the forces perpendicular to the two surfaces. I don't really know how to resolve them, and how F=μR comes into it.

2. May 30, 2012

### Infinitum

The question seems incomplete without mentioning what kind of prism it is...You cannot resolve the forces to anything useful. if you don't know the prism angle.

3. May 30, 2012

### azizlwl

We need a net force equal the weight of the prism, passing thru the centre of mass.
This net force is equal to the resultant of 2 forces, each from each finger.
The force from each finger is equal or less than maximum static friction between finder and prism.
The static friction is equal μN where N equal to force applied if it is applied perpendicularly to the plane of the prism.