Chapter 13 - Vibrations and Waves - Learning Path Questions and Exercises - Multiple Choice Questions - Page 483: 4

(b) at a maximum

The total energy of a particle in sum of its kinetic energy $\frac{mv^{2}}{2}$ and its potential energy $\frac{kx^{2}}{2}$. When the potential energy is minimum the kinetic energy is maximum and vice-versa. The potential energy is zero at the equilibrium position (x=0). So, the kinetic energy is maximum at the equilibrium position.