Work, Energy and Power

The sign of work done by a force on a body is important to understand. State carefully
if the following quantities are positive or negative:
(a) work done by a man in lifting a bucket out of a well by means of a rope tied to the
bucket.
(b) work done by gravitational force in the above case,
(c) work done by friction on a body
sliding down an inclined plane,
(d) work done by an applied force on
a body moving on a rough
horizontal plane with uniform
velocity,
(e) work done by the resistive force of
air on a vibrating pendulum in
bringing it to rest.