17. If y=0.2 sin(30x-400t) (SI units), the velocity of the wave is
(A)3/40 (m/s)
(B) 40π/3
(C) 60π/400 (m/s)
(D) 400/60π (m/s)
(E) 40/3 (m/s)
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統計: A(1), B(0), C(1), D(0), E(9) #3224663
統計: A(1), B(0), C(1), D(0), E(9) #3224663