【Daily Question】Theoretical Foundation 2020.05.27
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Multiple-choice question: A plane harmonic wave propagates in an elastic medium. At a certain instant, a particle in the medium is at its equilibrium position; at this time, its energy is (A) zero kinetic energy and maximum potential energy. (B) Kinetic energy is zero, potential energy is zero. (C) Kinetic energy is maximum, potential energy is maximum. (D) Kinetic energy is maximum, and potential energy is zero. Answer: C Hint: An extra reward will be given to those who can explain the solution process; the answer can be seen there!
The characteristic of C-wave energy is that kinetic energy and potential energy are in phase, reaching their maximum and minimum values at the same time. The particle is at its equilibrium position, where its kinetic energy is maximum and its potential energy is also maximum.
C. In a plane harmonic wave, the kinetic energy and potential energy of the particle vary in phase. At the equilibrium position, its velocity is at its maximum; since the equilibrium position is the center of either a region of high density or low density, the deformation is also at its maximum at this point, resulting in maximum values for both kinetic energy and potential energy. Therefore, the correct answer is C