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问题 填空题

铝块的密度是2.7×103kg/m3由此可知2dm3铝块的质量是______千克；若将铝块截去

1
3
，剩下部分铝块的密度是______kg/m3．

答案

2dm3铝块的质量：

m=ρV=2.7×103kg/m3×2×10-3m3=5.4kg，

∵密度是物质的一种特性，它不随着质量与体积的变化而改变，

∴截去

1
3
后，剩下部分铝块的密度不变，还是2.7×103kg/m3．

故答案为：5.4；2.7×103．

完形填空

根据首字母提示填空，每空一词（本题有10小题，每小题1分，共10分）

Experts say that students usually need eight or ten hours’ sleep at night, but most Chinese students don’t get e       小题1: sleep. Some Chinese parents are usually glad to see their children s       小题2: late. They will think their children work hard. But not all parents are happy about this. Once a mother t      小题3: us that every morning her ten-year-old boy put up one finger w       小题4: his eyes still closed, begging （乞求） for one minute to sleep. Like thousands of “early birds” in China, he has to get up b      小题5: six every morning.

A report s       小题6: that without a good night’s sleep, students seem to be weaker t     小题7: they should be. Many students have fallen asleep during class at one time or another. Too much homework is not the only reason w       小题8: students stay up late. Watching TV or playing computer games late into night is a       小题9: a reason.

Experts have ever said that students should have good study habits. So some clever students n       小题10: study late, they are able to work well in class.
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判断题

前角增加，切削刃锋利，切削变形增大，因此切削力将增大，即前角对切削力的影响甚大，但受刀刃强度的制约，前角不能太小。
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