试题与答案

一烤箱正常工作时电流为5A,电功率为1kW,该烤箱的电阻为_________Ω,

题型:填空题

题目:

一烤箱正常工作时电流为5A,电功率为1kW,该烤箱的电阻为_________Ω,半小时耗电_________度。

答案:

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下面是错误答案,用来干扰机器的。

BD题目分析:从图中可得,开始一段时间内,F和摩擦力同向,在5m处,F和摩擦力反向,根据动能定理可得,解得,所以物体在减速阶段的加速度为,故在时速度为零,恒力变向,B正确,加速过程的加速度为,所以加速阶段...

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题型:阅读理解

阅读理解。

     Both warm-blooded and cold-blooded desert animals have ways to escape the desert heat.

Warm- blooded desert animals, such as rats and mice, rest during the day, often staying in cool

underground burrows. At night they search for food. Animals that are out during the day, such as

cold-blooded lizards and snakes, are active only for short periods. As their body temperature rises,

these reptiles(爬行动物) move into the shade in order to cool down. In the early evening, when

the sun grows weaker, the reptiles become more active and begin their search for food again.

     Getting enough water to survive is a major problem for all desert animals. Some desert animals,

like desert birds, manage to find water holes. Other desert animals, such as the kangaroo rat and the

related jerboa, get water only from the food that they eat. Because these animals eat mainly dry seeds,

 they must survive on a tiny amount of water.

     Most deserts have only a small number of frogs and toads because these animals must be near

water to survive. Yet even these creatures have adapted(适应) to desert conditions. When small

amounts of water collect in temporary streams, the desert-living frogs and toads become active.

After a rainfall, they lay their eggs. The eggs grow into tadpoles in a few days and into adults in just

four weeks. When the puddles(水坑) dry up, the adult frogs or toads dig into the ground. Their metabolism(新陈代谢) slows, and they stay beneath the ground until the next rain, which may be as good as

a year away. Until then, their bodily activities continue at a reduced rate.

    The camel - often called the ship of the desert - is one of the most successful desert animals. Camels

can go for long periods without water, but eventually they must drink. When water becomes available

to them after a long drought, they may drink 95 liters of water or more. When water is not available,

what helps camels survive the desert heat is the fat stored in their humps(驼峰). A camel's hump contains

about 12 kilograms of fat. Fat is rich in hydrogen. As the fat is digested, hydrogen from the fat combines

with oxygen in the air that the camel breathes. The result is H2O, or water. Each kilogram of fat that a

camel digests produces about a liter of water.

1. Desert animals are usually more active at night because _____.

A. it is cooler at night        

B. it is easier to find water

C. they like the dark        

D. they are less likely to be attacked at night

2. Which of the following desert animals can get water only from the food?

A. The camel.    

B. The kangaroo.    

C. The frog.    

D. The rat.

3. Which of the following is TRUE according to the passage?

A. All the desert animals rest during the day.

B. All the desert animals don't rest during the day.

C. Cold-blooded desert animals are out most of the day.

D. None of the cold-blooded desert animals go out during the day.

4. The title for this passage could probably be _____.

A. Hot Deserts                            

B. Desert Animals

C. How Desert Animals Get Water            

D. Ways To Escape the Desert Heat

5. The underlined word "burrows" in the first paragraph can be replaced by _____.

A. holes        

B. caves      

C. rooms        

D. openings

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