质点作简谐振动,若速度最大值为vm=3×10-2m·s-1;振幅A=2×10-2m。若从速度为正的最大值开始计时,则振动的周期和初相位分别为:() A. B. C. D. 查看完整题目与答案 They are many on their farm. A. oxes B. chickens C. sheeps D. deers 查看完整题目与答案 与喉直...