单项选择题
A.v1=2v2,T2=2T1 B.v1=0.5v2,T1=2T2 C.v1=0.5v2,T2=2T1 D.v1=2v2,T1=2T2
A.1.1m/s B.1.15m/s C.1.5m/s D.1.6m/s
A.20 B.2.2 C.2.4 D.3.0