When is work done by a force negative ?

When is work done by a force postivie ?

When is work done by a force zero ?

How is work done by a force meaured ?

When work done by force of gravity is negative, then

When is the work done by gravity negative ?

The sign of work done by a force is important to understant. 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 the 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 froce 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.

Work done by a spning force is

Is work done by a non conservative force always negative ? Comment.