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问题 问答题

一辆汽车沿着平直公路从甲站开往乙站，起步阶段的加速度为2m/s2，加速行驶5s后匀速行驶2min，然后刹车，匀减速滑行50m后正好停在乙站．求这辆汽车

（1）匀减速过程的加速度大小

（2）从甲站运动到乙站的时间

（3）从甲站到乙站的平均速度大小．

答案

（1）加速5s后的速度为：v=a1

t 1
=10m/s

匀减速过程的初速度为10m/s，末速度为零，

由：

vt2-v2
2a
=s3，得：a=-1m/s2

匀减速过程的加速度大小为1m/s2，方向与初速度方向相反

（2）匀减速过程：vt=v+at3，得：t3=10s，

从甲站到乙站的时间为：t=t1+t2+t3=5+120+10=135s

（3）匀加速过程：s1=

1
2
a1t12=25m

匀速过程：s2=vt2=10×120=1200m

全过程：s=s1+s2+s3=1275m

全过程的平均速度大小为：

.
v
=
s
t
=
1275
135
=9.4m/s

答：（1）匀减速过程的加速度大小1m/s2；

（2）从甲站运动到乙站的时间是135s；

（3）从甲站到乙站的平均速度大小是9.4m/s．

阅读理解

There is a special kind of hotel in Quebec, Canada. It has a bar, a church, a shop and a small theater. These things are not unusual. But this hotel is only open from January till March every year. Why? Because it is made of ice and snow! When the weather gets warm, the hotel melts(融化) and closes. Every winter, the hotel owners build the hotel again.

Everything in the Ice Hotel is made of ice and snow. All the furniture, such as the tables and chairs, is made of ice. Even the beds are made of ice! So people use special sleeping bags on the ice beds. Inside the ice hotel, the temperature is about 27°F(-3°C)

When people sleep, the sleeping bags keep them warm. In the morning, they can have a hot breakfast. After breakfast, people can enjoy winter activities. They can go skiing or ice fishing. Or they can go skating in the dining room. At the end of the day, people can relax at the bar. They can have drinks in glasses made of ice.

Many people enjoy the Ice Hotel every year. But they can only enjoy it for a short time before it melts again.

小题1: Every year, this hotel is only open for        

A．four weeks

B．about three months

C．two seasons

D．about a year小题2:People can go      in the dining room after breakfast.

A．skiing.

B．skating.

C．fishing

D．swimming小题3: What's the best title of this passage?

A. An Unusual Hotel  B. A Warm Hotel  C. A Common Hotel   D An Old Hotel

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选择题

一 I'm not crazy. I really did see a UFO.

— Well. We'll _____ your story. [ ]

A. look into

B. look through

C. look over

D. look up

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