Q. A 30 gram mass is hanging from a spring whose unstretched length is 20 cm and whose spring constant is 2.5 N/m. In the list below are described 5 situations. In some of the situations, mass is at rest and remains at rest. In other situations, at the instant described, mass is in the middle of an oscillation initiated by a person pulling the mass downward 5 cm from its equilibrium position and releasing it. Ignore both air resistance and internal damping in the spring.

At the time the situation occurs, indicate whether the force vector requested points up (U), down (D), or has magnitude zero (0). Do not forget to describe the reasoning for each answer. Unsupported answers will receive no credit.

a) The force on the mass exerted by spring while the mass is at its equilibrium position and is at rest.

b) The force on the mass exerted by spring as the mass is at its equilibrium position and is moving downward.

c) The net force on the mass when the mass is at its equilibrium position and is moving upward.

d) The force on the mass exerted by the spring when it is at the top of its oscillation.

e) The net force on the mass when it is at the top of its oscillation.