There is a rigid solid sphere rolling without slipping on a horizontal surface. When we are taking the CM as the axis of rotation, we see that the Total Kinetic Energy comes out be as: KEtotal = KErotational + KEtranslational Here: KErotational = (1/2)ICMω2where ICM is the Moment of Inertia of the rolling body about its CM and ω is the angular velocity of the particles constituting the rolling rigid solid sphere about the CM. KEtranslational=(1/2)mV2CM Here we use KErotational because every particle is rotating about the CM and we use KEtranslational because everything including the CM is moving forward linearly with velocity say VCM. But when we take the point in contact with the ground as the instantaneous axis of rotation we only take KErotational. Suppose the point of contact is called P. Then KEtotal = KErotational = (1/2)IPω2 Where IP is the Moment of Inertia of the rolling body about the point of contact and ω is the angular velocity of the particles constituting the rigid rolling solid sphere about the point of contact. I read that, about instantaneous centre of rotation all the particles rotate about it as if that is the centre of rotation and that point is pinned/fixed. So it behaves like a disc pinned at the centre which is rotating (only rotating since it can't translate as it is pinned) about its centre (CM). But how is this possible for rolling without slipping? I mean even the point of contact is instantaneously at rest how can it behave as pinned forever so that particles don't seem to translate at all? Also, how can there be simultaneously 2 axis of rotation possible? The 2 namely being: The CM and the point of contact.