Explain negative value of work done.

Explanation

1) Suppose a ball is moving on a plain ground, will get stopped after sometime due to frictional force acting on it in opposite direction.

2) If the force on an object and acing displacement are in opposite directions then the work done by the force is taken as negative.
`W=-F times s`
3) If the work done has negative value, the body on which the work has been done losses energy.