问题 选择题

100g热水和50g冷水混合后(不考虑热量损失),则(  )

A.热水降低的温度等于冷水升高的温度

B.热水降低的温度小于冷水升高的温度

C.热水降低的温度大于冷水升高的温度

D.热水放出的热量小于冷水吸收的热量

答案

当将热水和冷水混合时,若不计热量损失,热水吸收的热量等于冷水放出的热量,即选项D是错误的;

设冷水温度从t01升高到t,吸收的热量为Q1;热水温度从t02降低到t,放出的热量为Q2

∵不计热损失,∴Q=Q

即:cm1(t-t01)=cm2(t02-t)

在上式中,C和t是相同的,由于冷水质量m1小于热水质量m2,故冷水所升高的温度(t-t01)大于热水所降低的温度(t02-t),故答案B是正确的.

故选B.

阅读理解

Many companies use guards and expensive alarm systems to protect their property(财产)。 Soon a new kind of protection will be used- robots. Engineers have been working on the first mobile robots for businesses. The robots will patrol(巡逻) factories, warehoues(仓库),and museums at night.

The mobile robots will move around slowly on wheels. They will be able to detect people through walls and pick up sounds, such as breaking glass. They can be fixed with lound sirens(警笛) to frighten thieves, or radios to signal police or guards.

To protect a building, a robot will have to move around without knocking into the walls. Information about the building will have to be stored in the robot’s small, built-in computer. A floor map could be programmed into the computer’s memory, for example.

A mobile robot will not be able to do everything. Unlike human guards, it will not be able to climb stairs, open doors, or move along rough ground. It won’t be able to tell the difference between friends and enemies. Because of that, people will have to be barred from the area it patrols.

One kind of mobile robot will be able to “sense” whether a chair or box has been moved and go around it. This robot will also judge size well enough so that it won’t send an alam if a cat crosses the room. And if someone tries to steal this robot, it will sound a loud, painful siren. The three-foot-tall robot will be hard to steal anyway. It will weigh about 200 pounds.

U.S companies pay almost $10 billion a year to protect their property with alarm systems and human guards. Mobile robots may be cheaper.

小题1:Why is the new kind of robots called mobile robots?

A.Because they are able to climb stairs.

B.Because they are able to send an alarm

C.Because they can open doors.

D.Because they can move around slowly on wheels小题2: How will a robot get directions for moving around a building?

A.From a human guard .

B.From a built- in computer.

C.From another robot .

D.From radio signals.小题3: What does the underlined word barred mean?

A.protected

B.allowed .

C.marked

D.prevented小题4: According to the text, a mobile robot will NOT be able to ___________.

A.sense whether something has been moved.

B.sense a cat crossing the room.

C.move over rough ground .

D.detect people through walls.小题5:This text mainly describes how robots will ___________.

A.protect the museum

B.set off a siren .

C.judge the size of a person.

D.patrol buildings.

不定项选择