Lifting a prism; coefficient of friction

AI Thread Summary
To lift a prism with a mass of 80 g using only its upper two faces, the coefficient of friction between the prism and skin is 0.4, which is crucial for calculating the required force. The equation F = μR indicates that the frictional force depends on the normal force applied. The forces acting on the prism must equal its weight, and since the forces are applied from two fingers, the net force is the sum of the forces from each finger. Without knowing the angle of the prism, resolving these forces becomes challenging, as the normal force must be perpendicular to the prism's surface for accurate calculations. The discussion emphasizes the need for additional information about the prism's geometry to determine the minimum lifting force accurately.
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Homework Statement


A prism has a mass of m = 80 g, and you wish to lift it, touching
the upper two faces only. If the coecient 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?


Homework Equations


F=μR


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.
 
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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.
 
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.
 
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