问题
问答题 简答题
轴承装配时，为什么必须先擦净辊颈再抹润滑油？
答案
参考答案：轴承在运转过程中，难免有颗粒杂质浸入辊颈部位，与润滑粘合在一起。当更换轧辊重新安装轴承时，必须擦净辊颈再抹润滑油，以防止因颗粒杂质卡两光滑表面而引起辊颈的早期磨损。
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轴承装配时，为什么必须先擦净辊颈再抹润滑油？
参考答案：轴承在运转过程中，难免有颗粒杂质浸入辊颈部位，与润滑粘合在一起。当更换轧辊重新安装轴承时，必须擦净辊颈再抹润滑油，以防止因颗粒杂质卡两光滑表面而引起辊颈的早期磨损。
| 阅读理解。 | ||||||||||||
| In 5 years,China plans to put its astronauts on the moon．But before that, a small machine rover (探月车) will be sent there．Recently, scientists in S hanghai showed a moon rover to the public． Scientists said they had spent four years making it．And they hoped the rover would be chosen to go to the moon． What is it like? The rover has six wheels (轮子)．It is meters high and 200 kilogrammes in weight．It can take videos and pictures of the moon．It can also get moon soil and study it． The rover can go as fast as 100 meters an hour．Experts say it can climb a 30-degree slope (斜坡)．It is smart and can get around rocks． According to researchers,the rover may need to be improved．The moon's gravity (重力) is only one--sixth that of the earth's．There are strong rays (射线) from the sun．The temperature also changes greatly there．It can be --180~C at night and 150~C in the daytime． China wild explore the moon．First,a spaceship will be sent to go around the moon．There will be no person in the spaceship．Then in 2012, a moon rover will be sent there．Finally,an astronaut will land on the moon sometime after 2017． The China--made moon rover looks very similar to NASA'S Mars rover．But there are differences
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| 1．If there is a box which is 60N on the earth,it is ________ N on the moon． | ||||||||||||
| A．60 B．10 C．about 100 D．about 600 | ||||||||||||
| 2．Which of the following is right? | ||||||||||||
| A．In 2012,an astronaut of China will land on the moon． B．Mars rover runs faster than Moon rover． C．Mar rover and Moon rover have the same power． D．China has made a Moon rover． |