通訊員從隊(duì)頭到隊(duì)尾時(shí)：s通+s隊(duì)=l隊(duì),即v通t1+v隊(duì)t1=l隊(duì),
得t1=l隊(duì)/(v通+v隊(duì))=200m/(2m/s+4m/s)=(100/3)s=33.3s
從隊(duì)尾返回隊(duì)頭時(shí)：s通-s隊(duì)=l隊(duì),即v通t2-v隊(duì)t2=l隊(duì),
得t2=l隊(duì)/(v通-v隊(duì))=200m/(4m/s-2m/s)=100s;
所以通信員在此過程中用的時(shí)間為t=t1+t2=133.3s