4.( )如圖所示.一足夠長(zhǎng)的固定斜面與水平面的夾角為 370 ,物體 A以初速度v1 從斜面頂端水平拋出,物體 B 在斜面上距頂端 L=15m 處同時(shí)以速度 v2 沿斜面向下勻速運(yùn)動(dòng),經(jīng)歷時(shí)間t物體A和物體B在斜面上相遇,則下列各組速度和時(shí)間中滿足條件的是(sin370=0.6,cos370=0.8,g=10 m/s 2 )
(A)v1=16 m/s,v2=15 m/s,t=3s.
(B)v1=16 m/s,v2=16 m/s,t=2s.
(C)v1=20 m/s,v2=20 m/s,t=3s.
(D)v1=20m/s,v2=16 m/s,t=2s.
3.( )球A從h高自由落下,與此同時(shí),在球A正下方球B以初速度自地面豎直上拋,若已知兩球在空中相遇,下面說(shuō)法錯(cuò)誤的是
A.h一定,V0越大,相遇時(shí)間越短 B.h一定,V0越大,相遇位置越高
C.h一定,V0越大,相遇時(shí)球A速度越大 D.兩球在相遇前運(yùn)動(dòng)時(shí)間為
2.( )甲、乙、丙三輛汽車以相同的速度同時(shí)通過(guò)某一路標(biāo),從此時(shí)開(kāi)始甲車一直做勻速直線運(yùn)動(dòng),乙車先加速后減速,丙車先減速后加速,它們經(jīng)過(guò)下一個(gè)路標(biāo)的速度又相同。則最先通過(guò)下一路標(biāo)的應(yīng)是
A.甲 B.乙 C.丙 D.條件不足,無(wú)法判斷
1.( )圖示為高速攝影機(jī)拍攝到的子彈穿過(guò)蘋果瞬間的照片。該照片經(jīng)過(guò)放大后分析出,在曝光時(shí)間內(nèi),子彈影響前后錯(cuò)開(kāi)的距離約為子彈長(zhǎng)度的1%~2%。已知子彈飛行速度約為500m/s,因此可估算出這幅照片的曝光時(shí)間最接近
A、10-3s B、10-6s C、10-9s D、10-12s
19.(★★★★★)-Who gave you this message?
-A man________himself Mr.Zhang.
A.called B.calling C.calls D.is called
18.(★★★★★)-Would you mind________me the dicionary?
-Of couse not.But it is ________my reach.
A.passing;out B.passing;beyond
C.to pass;far away D.to pass;out of
17.(★★★★★)Silver is the best conductor of electricity,copper________it closely.
A.followed B.to follow C.following D.being followed
16.(★★★★)With his son________,the old man felt unhappy.
A.to disappoint B.to be disappointed
C.disappointing D.being disappointed
15.(★★★★)________good,the food was soon sold out.
A.Tasted B.Being tasted
C.Tasting D.Having tasted
14.(★★★★)O’Neal works hard.He is often seen________heavily before his teammates have even arrived at practice.
A.sweated B.to be sweated
C.sweating D.being sweated
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