I am given a problem where I am to pick up the prism shown below by touching only the upper two faces. The coefficient of friction with each face is 0.4 and the mass of the prism is 30grams. What is the minimum force I must apply to each face in order to lift the prism?
The one thing I am stuck on are the directions of the force I apply with my fingers. I am not sure whether
a)the forces exerted by my fingers act horizontally inwards (which is slightly confusing me; theoretically, should horizontal forces not be able to counteract the downwards weight of the prism? And yet my calculations in this case give a force required of 0.61N)
b)or whether they act exactly normal to the surface (in which case i get 0.22N)
c)or whether they can act directly up the slope straight away, or at least with some upwards inclination to counteract the weight.