45:s=340x(2/2)=340m
46:t空=183.6/340=0.54s
t铁=0.54s-0.5s=0.04s
v铁=183.6/0.04=4590m/s
47:s车=12x2=24m
s声=340x2=680m
那么鸣笛时到高山的距离为352m,听到回声是时328m
45:s=340x(2/2)=340m
46:t空=183.6/340=0.54s
t铁=0.54s-0.5s=0.04s
v铁=183.6/0.04=4590m/s
47:s车=12x2=24m
s声=340x2=680m
那么鸣笛时到高山的距离为352m,听到回声是时328m