3.如圖①,在數(shù)軸上,點(diǎn)O為坐標(biāo)原點(diǎn),點(diǎn)A、B、C、D表示的數(shù)分別是-16、6、18、26.動(dòng)點(diǎn)P、Q同時(shí)出發(fā),動(dòng)點(diǎn)P從點(diǎn)B出發(fā),沿?cái)?shù)軸以每秒4個(gè)單位的速度向點(diǎn)C運(yùn)動(dòng),當(dāng)點(diǎn)P運(yùn)動(dòng)到點(diǎn)C后,立即按原來的速度返回.動(dòng)點(diǎn)Q從點(diǎn)C出發(fā),沿?cái)?shù)軸以每秒2個(gè)單位的速度向終點(diǎn)D運(yùn)動(dòng).當(dāng)點(diǎn)Q到達(dá)點(diǎn)D時(shí),點(diǎn)P也停止運(yùn)動(dòng),設(shè)點(diǎn)P的運(yùn)動(dòng)時(shí)間為t(t>0)秒.
(1)點(diǎn)A與原點(diǎn)O的距離是
.
(2)點(diǎn)P從點(diǎn)B向點(diǎn)C運(yùn)動(dòng)過程中,點(diǎn)P與原點(diǎn)O的距離是
(用含t的代數(shù)式表示).
(3)點(diǎn)P從點(diǎn)B向點(diǎn)C運(yùn)動(dòng)過程中,當(dāng)點(diǎn)P與原點(diǎn)O的距離恰好等于點(diǎn)P與點(diǎn)Q的距離時(shí),求t的值.
(4)在點(diǎn)P、Q的整個(gè)運(yùn)動(dòng)過程中,若將數(shù)軸在點(diǎn)O和點(diǎn)P處各折一下,使點(diǎn)Q與點(diǎn)A重合,如圖②所示,當(dāng)所構(gòu)成的三角形OPQ中恰好有兩條邊相等時(shí),求t的值.