一列沿x轴方向传播的简谐横波,某时刻的波形如图中的实线所示,经过2 s后波形如图中虚线所示。求这列波的波速。 答案:解:由图可知:波长=8m 若波沿x轴正方向传播:△t=(n+)T v= 解得:v=4n+1 (n=0,1,2,3……) 若波沿x轴负方向传播:△t=(n+)Tv= 解得:v=4n+3 (n=0,1,2,3……)Jim as well as his friends ______
to blame for breaking the door last week.
A. were B. is
C. was D. are.