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

Is the spring force a conservative or a non-conservative force?

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 $U$ between two molecules as a function of distance $x$ between them is shown. $A, B, C$ are points for which $x = 0.6 \mathring{A}, 1.2 \mathring{A}, 1.8 \mathring{A}$ respectively. At $A, B, C$,the force between the two molecules is:

The potential energy of a certain particle is given by $U = \frac{1}{2}\,(x^2 - z^2)$. The force on it is:

$Assertion$ : Frictional forces are conservative forces.
$Reason$ : Potential energy can be associated with frictional forces.