3.如圖,△ABC中,∠ACB=90°,AC=6cm,BC=8cm,點(diǎn)P從A點(diǎn)出發(fā)沿A-C-B路徑運(yùn)動(dòng),終點(diǎn)為B點(diǎn);點(diǎn)Q從B點(diǎn)出發(fā)沿B-C-A路徑運(yùn)動(dòng),終點(diǎn)為A點(diǎn).點(diǎn)P和點(diǎn)Q分別以1cm/s和3cm/s的速度同時(shí)開始運(yùn)動(dòng),兩點(diǎn)到達(dá)相應(yīng)的終點(diǎn)時(shí)分別停止運(yùn)動(dòng).若分別過點(diǎn)P和Q作PE⊥l于E,QF⊥l于F.當(dāng)△PEC與△QFC全等時(shí),點(diǎn)P的運(yùn)動(dòng)時(shí)間t為 s.