A puck of mass 0.40kg travels around a rectangular path on a perfectly horizontal air table. The path consists of the following segments in order:
AB: 0.50m east across a felt patch where the coefficient of kinetic friction is 0.30;
BC: 0.80m north on a frictionless surface;
CD: 0.50m west on the same frictionless surface;
DA: 0.80m south on the same frictionless surface, returning to point A.
Neglect air resistance.
(a) State the net work done by gravity over the complete loop.
(b) Calculate the net work done by kinetic friction over the complete loop. Provide each answer with its sign.