Question

A ball is rolling on a mountain of the shape as shown in the picture. At which place will the ant be in stable equilibrium?

• A. A
• B. A and D
• C. C
• D. E

Answer 1

The correct option is D E

When a particle is displaced from its position of stable equilibrium, a restoring force pulls it back to the equilibrium position, in a way keeping it "stable”. In the given question that happens only at E. A small displacement from the equilibrium position of E would cause the ball to roll back to E. This is something that wouldn't happen at A, B, C or D. In fact, A and D are points of unstable equilibrium. An unstable equilibrium in most simple terms is an equilibrium point from where if a body is displaced, it moves even further away. B is not a position of equilibrium. C is a position of neutral equilibrium. In displacing a body from a position of neutral equilibrium it will neither be pulled back nor pushed away from it.