Hello. I'm an intro physics student, who needs help with physics problem, because my graduate student refuses to help anybody in my class anyway... here is my first question on rotational kinetic energy 1) "A uniform disk of mass M and radius R can rotate freely about a horizontal axis through its center and perpendicular to the plane of the disk. A small particle of mass m is attached to the rim of the disk at the top, directly above the pivot. The system is given a gentle nudge, and the disk begins to rotate." a) "What is the angular velocity of the disk when the particle is at its lowest point?" b)"At this point, what force must be exerted by the disk on the particle to keep it stuck to the disk" ..... First of all where should I start with part a)? And how does rotational kinetic energy apply to this problem. Second, how do I find the force for part b) .... My second question is.... 2) "A uniform ring 1.5 m in diameter is pivoted at one point on its perimeter so that it is free to rotate about a horizontal axis. Intially, the line joining the support point and the center is horizontal." a) "If the ring is released from rest, what is its maximum angular velocity?" b) "What minimum initial angular velocity must it be given if it is to rotate a full 360 degrees?" ... Once again any tips would be helpful... I appreciate it. Thanks.