1. The problem statement, all variables and given/known data In the given arrangement a sphere of mass "m" rolling on a rough surface strikes a rough inclined plane. Find the velocity of centre of mas and the angular velocity of sphere if just after collision, it starts ascending up the incline plane and performs rolling. http://img228.imageshack.us/img228/7488/picw.jpg [Broken] 3. The attempt at a solution When the sphere is just about to ascend the incline plane, it will be in contact with two surfaces and hence two contact forces will act on it just at the moment when it is about to ascend. But both of these forces will pass through the centre of mass, so their net torque about centre of mass will be zero. The angular velocity omega will remain same. To find the velocity of the sphere I apply conservation of momentum about point P (with which the sphere will be in contact at the time of ascending). Initial angular momentum (mVoRcos (theta)+ I*omega)=Final momentum(mV'R+I*omega) V'=Vo cos (theta) Where is the flaw in my solutions?