2. A mass m is released from a height H slides on a frictionless surface that becomes a vertical circle of radius R. What is the minimum value of H for the particle not to loose contact with the circle. If it is released from twice the minimum height, what is the force exerted by the track on the block at the highest point H 3. A ball of mass m moves in a a vertical circle at the end of a string. What is the ratio of tension at the top of the circle compared to tension at the bottom in terms of m 4. A small object of mass m slides with a constant speed v down an incline making an angle 8 with horizontal. Derive an expression for the energy dissipated by friction during the time interval At A hole is drilled from the surface of the earth to its center. The gravitational force on a particle of mass m which is inside the earth at a distance r from the center (r