Hello. The problem is this, what happens to angular momentum, tangential velocity and centripetal force when you change the center of rotation. For example, if we have rotating hinged arm, weight at the end, with certain angular momentum and tangential speed etc. which then gets stopped at hinge, but the 2nd part of the hinge can still rotate thus giving half the radius and a different center of rotation. Normaly, if you decrease radius (for example weight at the end of the string and you pull the string decreasing radius) you can assume there´s no torque and because of that L=mrv, L/m=rv and from there see that radius and velocity are inversely proportionate. As far as i know the angular momentum is always relative to center of rotation, so when the center of rotation shifts, can you still use the above formula and others like it, or does something wierd happen? Intuition says it´s the same, but i haven´t been able to find proper source to prove it. So does anyone know a site/book/thing where it´s discussed?