3.如圖所示,在△ABC中,AB=AC=24cm,BC=18cm,∠B=∠C,D為AB的中點(diǎn),點(diǎn)P在線(xiàn)段BC上由點(diǎn)B出發(fā)向點(diǎn)C運(yùn)動(dòng),同時(shí)點(diǎn)Q在線(xiàn)段CA上由點(diǎn)C出發(fā)向點(diǎn)A運(yùn)動(dòng),設(shè)運(yùn)動(dòng)時(shí)間為t(s).(1)若點(diǎn)P與點(diǎn)Q的速度都是3cm/s,則經(jīng)過(guò)多長(zhǎng)時(shí)間△BPD與△CQP全等?請(qǐng)說(shuō)明理由.
(2)若點(diǎn)P的速度比點(diǎn)Q的速度慢3cm/s,則經(jīng)過(guò)多長(zhǎng)時(shí)間△BPD與△CQP全等?請(qǐng)求出此時(shí)兩點(diǎn)的速度.
(3)若點(diǎn)P、點(diǎn)Q分別以(2)中的速度同時(shí)從點(diǎn)B,C出發(fā),都按逆時(shí)針?lè)较蜓亍鰽BC三邊運(yùn)動(dòng),則經(jīng)過(guò)多長(zhǎng)時(shí)間點(diǎn)P與點(diǎn)Q第一次相遇?相遇點(diǎn)在△ABC的哪條邊上?請(qǐng)求出相遇點(diǎn)到點(diǎn)B的距離.