The given plot shows the variation of U, the potential energy of interaction between two particles with the distance separating them r,

Options

A. 1 and 2
B. 1 and 4
C. 2 and 4
D. 2 and 3

Answer

C

Explanation

Conservative force is equal to negative gradient of potential energy function so `vecF=-(dU)/(dr)`
At point of equilibrium Force is zero and so `(dU)/(dr)=0` i.e at point of equilibrium slope of (U-r) curve must be zero. At C,P.E is minimum so C is a point of stable equilibrium.
Between E and F slope of potential energy curve is negative so
By `F=-(dU)/(dr)`, force is positive i.e.repulsive.