Question

一列隊(duì)伍長(zhǎng)50m，跑步速度是2.5m/s，隊(duì)伍全部通過(guò)一長(zhǎng)100m的涵洞，需要的時(shí)間是（ ）
A．60s
B．50s
C．40s
D．20s

Answer 1

【答案】分析：已知隊(duì)伍的長(zhǎng)度和涵洞的長(zhǎng)度，隊(duì)伍過(guò)涵洞經(jīng)過(guò)的距離為隊(duì)伍長(zhǎng)加上涵洞長(zhǎng)，跑步速度已知，根據(jù)公式t=可求需要的時(shí)間．
解答：解：隊(duì)伍過(guò)涵洞經(jīng)過(guò)的距離為S=S_隊(duì)+S_洞=50m+100m=150m，
需要的時(shí)間t===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)是隊(duì)伍所走路程的計(jì)算，這也是本題的重點(diǎn)．