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（14分）一平板车的质量M=100kg，停在水平路面上，车身的平板离地面的高度h=1.25m.一质量m=50kg的物块置于车的平板上，它到车尾端的距离b=1.00m，与平板间的动摩擦因数μ=0.20，如图所示．今对平板车施一水平方向的恒力，使车向右行驶，结果物块从车板上滑落，物块刚离开车板的时刻，车向前行驶的距离s0=2.0m，不计路面与平板车间以及轮轴之间的摩擦，取g=10m/s2，求：

(1) 物块没有离开平板车时物块的加速度和物块刚要离

开平板车时平板车的速度．   

(2) 物块落地时，落地点到车尾的水平距离是多少？

答案

(1)4M/S(2)1.625M

（1）以m为研究对象进行分析，m在车板上的水平方向只受一个摩擦力f′的作

用，f=μmg，根据牛顿第二定律知f=ma1    a1=μg=0.20×10m/s2=2m/s2    （2分）

如图，m从A点运动到B点，做匀加速直线运动，sAB=s0-b=1.00m，运动到B点的速度υB为：  

υBm/s="2m/s  " （2分）

物块在平板车上运动时间为t1=υB/ a1=2/2=1s，在相同时间里平板车向前行驶的距离s0=2.0m，则有

s0=，所以平板车的加速度 m/s2   

此时平板车的速度为m/s   （2分）

（2）m从B处滑落时，以υB为初速度做平抛运动，落到C的水平距离为s1，下

落时间为t2，如图所示，

则      s  

 m ="1.0" m            （2分）

对平板车M，在m未滑落之前，水平方向受二力作用，即F和物块对平板车的摩擦力f，二者方向相反，平板车加速度为a2，由牛顿第二定律得：F- f=Ma2

则有：F =Ma2+ f =（100×4+0.2×50×10）N ="500N      " (2分)

当m从平板车的B点滑落以后，平板车水平方向只受F作用，而做加速度为

a3的匀加速运动，由牛顿第二定律得：F=Ma3  即m/s2   （2分）

在m从B滑落到C点的时间t=0.5s内，M运动距离s2为m

物块落地时，落地点到车尾的水平距离s为                                                     

s=s2-s1=（2.625-1）m="1.625m      " (2分)

阅读理解

阅读短文，选择正确答案。

     News 1

     A Taiwan's actress Lin Chi-ling won the Asia Star Award at the 2009 Asia Model Festival Awards (AMFA) in

Seoul (首尔) on January 15, 2009.

     News 2

     Forty-six ships had a big party in Qingdao on April 23, 2009. They came from 15 countries around the

world. They came for the birthday party of the Chinese navy. The Chinese navy is 60 years old! The Chinese

ships and weapons are all the work of Chinese engineers. The Chinese navy had 26 ships at the beginning. There

are more than 200 ships now.

     News 3

     CHENGDU, Sichuan, May 11-On Monday, Hong Kong movie star Jackie Chan came to Beichuan Middle

School. He joined the students who survived (幸存) last year's earthquake, singing with them to help the

teenagers on the day before the quake's anniversary (周年纪念). Chan opened a national flag covering 5,000

square meters on the school playground.

     More than 1,000 students and teachers of the school were dead or missing in the earthquake on May 12 last

year. The new school will begin to be rebuilt with the money from all over the world on Tuesday.

1. The 2009 Asia Model Festival Awards were held in             . [ ]

A. Seoul

B. Taiwan

C. Qingdao

D. Sichuan

2. When was the Chinese navy founded? [ ]

A. On January 15, 2009.

B. On April 23, 2009.

C. On April 23, 1949.

D. On May 11, 2008.

3. Jackie Chan came to Beichuan to             .[ ]

A. go sightseeing

B. take part in the quake's anniversary

C. make a film

D. play with the children

4.               students and teachers of Beichuan Middle School were dead or missing in the May12th earthquake

    last year. [ ]

A. Over 1, 000

B. Less than 1, 000

C. More than 5, 000

D. At most 5, 000

5. Which of the following is TRUE according to the passage? [ ]

A. Lin Chi-ling, a Korean actress, won the Asia Star Award.

B. 200 ships celebrated the birthday of the Chinese navy.

C. The Chinese ships and weapons were made by Chinese engineers.

D. Beichuan Middle School will be rebuilt next year.

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填空题

南唐后主（）填词技艺娴熟，情境别致，被誉为“词中之帝”。
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