Question

The given plot shows the variation of $U$, the potential energy of interaction between two particles with the distance separating them $r$.
1. B and D are equilibrium points.
2. C is a point of stable equilibrium.
3. The force of interaction between the two particles is attractive between points C and D and repulsive between D and E.
4. The force of interaction between particles is repulsive between points E and F.
Which of the above statements are correct?

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

Answer 1

Answer: (D)

2 and 4

Force of interation is the negative of slope of graph of potential energy v/s distance between the particles.

$F=-\frac{dU}{dr}$

Hence, $C$ and $E$ are points of stability. For stable equilibrium, potential energy should be minimum. Hence, $C$ is a point of stable equilibrium.

Negative force means attraction and positive force means repulsion. Hence, force is repulsive between $E$ and $F$ and attractive between $C$ and $E$.