Question

一列隊(duì)伍長50米，行進(jìn)速度2.5m/s，經(jīng)過一座100m的涵洞，當(dāng)隊(duì)伍全部穿過涵洞時(shí)，總共需要（　�。�

• A、60s
• B、40s
• C、50s
• D、80s

Answer 1

分析：當(dāng)隊(duì)伍全部穿過涵洞時(shí)，隊(duì)伍經(jīng)過的距離為隊(duì)伍的長度與涵洞長度之和，行進(jìn)速度已知，根據(jù)公式t=

S

V

可求所需的時(shí)間．

解答：解：隊(duì)伍從隊(duì)首進(jìn)洞到隊(duì)尾離洞，一共行走的路程為S=S_隊(duì)+S_洞=50m+100m=150m，
當(dāng)隊(duì)伍全部穿過涵洞所需要的時(shí)間為t=

S

V

=

150m

2.5m/s

=60s．
故選A．

點(diǎn)評(píng)：本題考查時(shí)間的計(jì)算，關(guān)鍵是速度公式及其變形的靈活運(yùn)用，難點(diǎn)在于路程的確定，這也是本題的重點(diǎn)．