http://i.imgur.com/0RtN9Ui.png?1 I am trying to find the linear velocity of the sphere as it leaves the cliff. 2. Relevant equations: Moment of inertia of a sphere: I= 2/5 mr2 3. My attempt at a solution: I know that I am supposed to solve this through the conservation of energy, but would I not have to account for friction somehow since it is rolling without slipping? I know how to find the kinetic and potential energies at both points but the solutions manual (i know, i know, i cheated) says nothing about accounting for the non-conservative force of friction that is necessary for rolling without slipping. Either way, without friction I have U-initial: 0 K-initial= 1/2 mv^2+(1/2)*(2/5*m*r^2)*v^2/r^2 k-initial= 1/2 mv^2+1/5 mv^2 k-initial: 7/10 mv^2 and for U-final: mgh K-final: 7/10 mvfinal^2 Could i just set these equal to each other and get the answer? No friction needed?