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在一些中学物理复习资料中,常常见到这样一道题:在如附图所示的一列简谐波的波形曲线中,沿波的传播方向有A、B、C、D、E、F、G…等质点,问在图示的时刻,哪些质点的动能最大?哪些质点的势能最大?给出的答案是:A、C、E、G…各质点的动能最大,B、D、F…各质点的势能最大。这个答案对于势能来说是错误的。因为经过认真分析后不难发现,这时A、C、E、G…各质点不仅动能最大,势能也最大;B、D、F…各质点不仅动能为零,势能也为零。从波的图象可以看出,在波传播的某一时刻,处于平衡位置的媒质质点不仅具有最大的速度,也恰好处于最大的形变状态。这一点无论对纵波或横波都是正确的。拿纵波来说,它的波形曲线跟x轴的交点对应于它的密部中央和
In some secondary school physics review materials, it is common to see such a problem: In a waveform of a harmonic wave as shown in the figure, there are A, B, C, D, E, F, G along the direction of wave propagation. ...etc. The mass point, asked at the time of the illustration, which particles have the greatest kinetic energy and which particles have the greatest potential energy? The answer given is: A, C, E, G... The kinetic energy of each particle is the largest, B, D, F... The maximum potential energy of the particle. This answer is wrong for potential energy. Because after careful analysis it is not difficult to find, then A, C, E, G... Each particle not only has the largest kinetic energy, but also the largest potential energy; B, D, F... Each particle not only has zero kinetic energy, but also zero potential energy. From the image of the wave, it can be seen that at some point in the propagation of the wave, the medium particle in equilibrium has not only the maximum velocity but also the maximum deformation state. This is true for both longitudinal and transverse waves. In the case of longitudinal waves, the intersection point of its sinusoidal curve with the x-axis corresponds to its central part of the