On book Classical Dynamics of Particles and Systems (5th Edition), from Marion, on problem 11.20, it stats that a rod starts to tipping over from its vertically position and we need to find the angular velocity of it after it hits the ground. My question is why we do not consider the linear velocity of the center of mass an so its kinect energy, like we do in problem 11.11.

11-20. A uniform rod of length b stands vertically upright on a rough floor and then tips over. What is the rod's angular velocity when it hits the floor?Rotation Translation my2# according to given situation in the Question initial situation . in the initial stage the rod is standing as shown in the figure, then it's Kinetic energy is zero f potential energy is mgo . in the final state, the rods hits the I = mb 2 final floor it's potential energy is zeno 3 Situation + it's Kinetic energy is JIW2 - applying energy conservation initial potential energy - U. = mgo final potential energy= U. = 0 (6cz lcoat on ground ) lefelionce point 2 x ( mb 2] w 2 = my by =) w 2 - m/g 6 w 2 39 3 Ans