如圖所示,在梯形ABCD中,AD∥BC,∠B=90°,AD=24cm,BC=26cm,動(dòng)點(diǎn)P從點(diǎn)A出發(fā)沿AD方向向點(diǎn)D以1cm/s的速度運(yùn)動(dòng),動(dòng)點(diǎn)Q從點(diǎn)C開始沿著CB方向向點(diǎn)B以3cm/s的速度運(yùn)動(dòng).點(diǎn)P、Q分別從點(diǎn)A和點(diǎn)C同時(shí)出發(fā),當(dāng)其中一點(diǎn)到達(dá)端點(diǎn)時(shí),另一點(diǎn)隨之停止運(yùn)動(dòng).
(1)經(jīng)過多長(zhǎng)時(shí)間,四邊形PQCD是平行四邊形?
(2)經(jīng)過多長(zhǎng)時(shí)間,四邊形PQBA是矩形?
(3)經(jīng)過多長(zhǎng)時(shí)間,當(dāng)PQ不平行于CD時(shí),有PQ=CD.