Question

give one example where work down by an object is negative

Answer 1

When a body is dragged along a rough surface, then work done by frictional force is negative,because the frictional force acts in direction opposite to that of the displacement

Answer 2

Hi Friend !!

Consider a body (a monkey ) climbing up a tree!

Here the force acting on the monkey due to its weight is downwards.
But the monkey is climbing upwards. So the displacement is clearly in the upward direction .

We know that work done
=Fxs cos180° ( here we take cos 180° since the force acting on the body and the displacement vectors lie in a straight line but in opposite directions.)
= Fs x (-1)
= -Fs

The negative sign indicates that negative work has been done in this case.

Hope that clears your doubts friend !