In simple harmonic motion of a mass on a horizontal spring, when the mass passes through the turning points, what is its speed?

In simple harmonic motion of a mass on a horizontal spring, when the mass passes through the turning points, what is its speed?

• A. Speed is zero at turning points; maximum at equilibrium
• B. Speed is maximum at turning points
• C. Speed is constant
• D. Speed is independent of position

Answer: (A)

In simple harmonic motion, energy keeps shifting between kinetic and potential. The turning points are the farthest displacements, where the mass is about to change direction. At those instants the velocity is zero, so the speed is zero because all the energy is stored as the spring’s potential energy and none as kinetic energy. As the mass moves toward the center, potential energy converts to kinetic energy, so the speed increases and is greatest as it passes through the equilibrium position where the displacement is zero and the potential energy is minimum.

In simple harmonic motion, energy keeps shifting between kinetic and potential. The turning points are the farthest displacements, where the mass is about to change direction. At those instants the velocity is zero, so the speed is zero because all the energy is stored as the spring’s potential energy and none as kinetic energy. As the mass moves toward the center, potential energy converts to kinetic energy, so the speed increases and is greatest as it passes through the equilibrium position where the displacement is zero and the potential energy is minimum.