Is the work done by non-conservative forces always negative? Discuss.

Write a few remarks on conservative forces.

The variation of potential energy $U$ of a system is shown in the figure. The force acting on the system is best represented by:

In the case of non-conservative forces,the following statement is correct.

If potential energy is given by $U = \frac{a}{r^2} - \frac{b}{r}$,find the maximum force. (Given $a = 2, b = 4$)

The potential energy of an object of mass $m$ moving in the $xy$ plane in a conservative field is given by $U = ax + by$,where $x$ and $y$ are position coordinates of the object. Find the magnitude of its acceleration.