1. The problem statement, all variables and given/known data Suppose a uniform sphere of mass M and radius R is placed on a rough horizontal surface. It rolls without slipping. We can apply 2 equations. 1) considering the torque due to frictional force about the centre of mass, fR=I(alpha) here alpha=a/R as the it is in pure rolling motion so f=2Ma/5 2)considering the linear motion, Ma=f why are 1 and 2 contradicting.?