State the sign of work done by a force in the following.
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 case.

Work done W = FScos$\mathrm{\theta }$.... (1)
a) As the force and displacement are in the same direction ($\mathrm{\theta }$ = 0) work done is positive.

b) As the force and displacement are in the opposite direction, ($\mathrm{\theta }$=180°) work done is negative.