A 1.6-lb collar is attached to a spring and slides without friction along a circular rod in a vertical plane. The spring has an unstretched length of 6 in. The collar is released from being held at A, and it passes ponit B with a speed of 16.0 ft/s. Determine the spring constant. The circular rod is kept from moving.

Electromagnetic induction. a coil of wire contains n turns and has an electrical resistance r. the radius of each turn is a. initially, inside the coil there exists a uniform magnetic field of magnitude b0 parallel to the axis of the coil. the magnetic field is then reduced slowly. the current induced in the coil is i. how long does it take for the magnitude of the uniform field to drop to zero?