State the sign of work done by a force in the following .
work done by the resistive force of air on a vibrating pendulum in bringing it to rest .

Explanation

Workdone `W = vec(F)* vec(S) = FS cos theta " where " theta ` smaller angle between force `vec(F) ` and displace- ment `vec(S)`
The direction of resistive force is opposite to the direction of the bob i.e. `theta = 180^(@)` . Hence workdone, in this case, is negative.