Hi people! I have a real life problem that i can't solve....Im trying to figure out the tangencial speed or angular velocity of a hatch at the moment it is about to close (initially it was closed). The hatch has been accelerating due to gravity. It looks much as a pendulum to me. But, it gets more complicated when you add the fact that the hinge of this hatch, has friction that can't be ignored. - Can i calculate this friction? - Can anybody help me to get a mathamatical model of this system? (maybe just doing energy balance). - And the main question...How can i calculate the angular velocity at the moment of the impact with the frame? Imagine something like this (http://www.getprice.com.au/images/uploadimg/592/_1_skyspan_metal_hatch.jpg [Broken]) Thanks.