A:先是到头:t1=s/v=3200/(18-2)=200s
再是到尾:t2=s/v=3200/(18+2)=160s
加起来:200s+160s=360s=6min
B:S2=vs=(10+15)*6s=150m
t=s/v=150/(15-10)=30s
A:先是到头:t1=s/v=3200/(18-2)=200s
再是到尾:t2=s/v=3200/(18+2)=160s
加起来:200s+160s=360s=6min
B:S2=vs=(10+15)*6s=150m
t=s/v=150/(15-10)=30s