6.-Mike, what did our monitor say just now?
-Every boy and every girl as well as teachers who to visit the museum asked to be at the school gate before 6:30 in the morning.
A. is; is B. are; is C. is; are D. are; are
5. Tom as well as two of his friends ________ to the concert last night A. has been invited B. had been invited
C. were invited D. was invited
4. A variety of books _____________ the children of different ages.
A. are interested in B. is interested in
C. are intending for D. is intending for
3. This special strain of rice ___________ one-third more of the crop in the same field.
A. makes possible to produce B. makes it possible to produce
C. make possible producing D. make it possible producing
2. The rich_____ not always happy. .
A. is B. are C. has D. have
1. The teacher, with 6 girls and 8 boys of her class, _______ visiting a museum when the earthquake struck.
A. was B. were C. had been D. would be
12.
图4-1-30
如图4-1-30所示,在距地面80 m高的水平面上做匀加速直线运动的飞机上每隔1 s依次放下a、b、c三物体,抛出点a、b与b、c间距分别为45 m和55 m,分别落在水平地面上的A、B、C处.求:
(1)飞机飞行的加速度;
(2)刚放下b物体时飞机的速度大小;
(3)b、c两物体落地点BC间距离.
解析:(1)飞机水平方向上,由a经b到c做匀加速直线运动,由Δx=aT2得,a===10 m/s2.
(2)因位置b对应a到c过程的中间时刻,故有vb==50 m/s.
(3)设物体落地时间为t,由h=gt2得:t= =4 s,BC间距离为:BC=bc+vct-vbt,
又vc-vb=aT,得:BC=bc+aTt=95 m.
答案:(1)10 m/s2 (2)50 m/s (3)95 m
10.
图4-1-28
(2010·西安质检)质量为0.2 kg的物体,其速度在x、y方向的分量vx、vy与时间t的关系如图4-1-28所示,已知x、y方向相互垂直,则( )
A.0-4 s内物体做曲线运动
B.0-6 s内物体一直做曲线运动
C.0-4 s内物体的位移为12 m
D.4-6 s内物体的位移为2 m
答案:AD
9.
图4-1-27
乒乓球在我国有广泛的群众基础,并有“国球”的美誉,中国乒乓球的水平也处于世界领先地位.现讨论乒乓球发球问题,已知球台长L、网高h,假设乒乓球反弹前后水平分速度不变,竖直分速度大小不变、方向相反,且不考虑乒乓球的旋转和空气阻力.若球在球台边缘O点正上方某高度处以一定的速度被水平发出(如图4-1-27所示),球恰好在最高点时越过球网,则根据以上信息可以求出( )
A.发球的初速度大小 B.发球时的高度
C.球从发出到第一次落在球台上的时间 D.球从发出到对方运动员接住的时间
解析:由运动对称性可知,发球位置距球台的高度等于网高h,发球点到球第一次落在台上P1点的水平距离为L/4,根据平抛运动的规律h=gt2,=v0t,由此两式可求出发球时的速度v0和球从发出到第一次落在台上的时间t,所以A、B、C项均正确;但由于不知道对方运动员在何处接住球,故无法求出总时间,D项错误.
答案:ABC
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