1. The problem statement, all variables and given/known data A small block slides from rest from the top of a frictionless sphere of radius R.How far below the top,x,does it lose contact with the sphere?(Sphere doesn't move) 3. The attempt at a solution The angle subtended by the block at the centre of the sphere can be taken as theta.If the x axis is considered tangential to the surface and hence y axis in the direction of the normal force,this problem can be solved,when combined with the conservation of energy. N-mg cos(theta)=-mv^2/R and mgR(1-cos(theta))=1/2mv^2 Answer is R/3. My question is,how do you solve this problem if the axes are taken "upright",instead of being inclined.i.e,the y-axis is vertical and x-axis is horizontal.