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:
1. work done by a man in lifting a bucket out of a well by means of a rope tied to the bucket.
2. work done by gravitational force in the above case.
3. work done by friction on a body sliding down an inclined plane.
4. work done by an applied force on a body moving on a rough horizontal plane with uniform velocity.
5. work done by the resistive force of air on vibrating pendulum in bringing it to rest.
