I'm trying to calculate the rotation of a rigid body due to a force applied to a single point on the body. This application is for 3D game programming. I understand how to find the axis of rotation by calculating the cross product of the point of intersection & the vector between the center of the rigid body and the point of intersection(vecPtoC). My question is this: If the rigid body has a certain mass, how do I determine how much force to apply in order to cause the body to rotate? If the force applied to the body is too small, the body should not rotate. Also, if the force applied to the body is great enough to rotate the body, how much does the body rotate due to the force?