Suppose we have a rod standing vertically and then slightly disturbed so it begins to fall. After it falls through some height or angle assuming a clockwise rotational fall I can see that the left end is sliding on the surface ( for simplicity I'm ignoring friction ) horizontally. Here I assume that I know the change in height although knowing length of rod and angular displacement would work as well. In that case, would I be right to say that the change in PE equals 1/2 I w^2 + 1/2 M v^2 For I , v and w at the Center of mass ? While that is normally the case for combined translation and rotation, I'm having doubts using that expression here as the leftmost end doesn't seem to rotate about the CM, it's sliding instead. Should I try to take the CM's source of torque ( the normal force on the leftmost point of contact ) and work from there to obtain some results ?