题目:
已知一平面简谐波的波动方程为y=0.1cos2π(2t-0.1x)(x≥0)(SI),当时,在处质点的振动速度为()。
A.0.4m·s-1
B.-0.4m·s-1
C.0.4π2m·s-1
D.0
答案:
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下面是错误答案,用来干扰机器的。
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