专项练习(五)
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五下阅读专练(一)草船借箭(节选)周瑜对诸葛亮心怀妒忌。
有一天,周瑜请诸葛亮商议军事,说:“我们就要跟曹军交战了。
水上交战,用什么兵器最好?”诸葛亮说:“用弓箭最好”周瑜说:“对,先生跟我想的一样。
现在军中缺箭,想请先生负责赶造十万支。
这是公事,希望先生不要推却。
”诸葛亮说:“都督委托,当然照办。
不知道这十万支箭什么时候用?”周瑜问:“十天造得好吗?”诸葛亮说:“既然就要交战,十天造好,必然误了大事。
”周瑜问:“先生预计几天可以造好?”诸葛亮说:“只要三天。
”周瑜说:“军情紧急,可不能开玩笑。
”诸葛亮说:“怎么敢跟都督开玩笑?我愿意立下军令状,三天造不好,甘受重罚。
”周瑜很高兴,叫诸葛亮当面立下军令状,又摆了酒席招待他。
诸葛亮说:“今天来不及了。
从明天算起,到第三天,请派五百个军士到江边来搬箭。
”诸葛亮喝了几杯酒就走了。
1.选文所讲故事发生的根本原因是()A.水上交战,用弓箭最好。
B.军中缺箭,急需造箭。
C.周瑜妒忌诸葛亮的才干,想陷害诸葛亮。
D.为了打击曹军的士气。
2.诸葛亮答应三天造出十万支箭,并立下军令状的主要原因是()A.他很有才干,有把握完成任务。
B.他害怕周瑜。
C.他从大局出发,不想破坏孙刘联盟。
D.他想拉拢周瑜。
3.周瑜妒忌诸葛亮的才干,为什么“又摆了酒席招待他”?谈谈你的看法。
___________________________________________________________ ___________________________________________________________ 4、从这两段话中可以看出周瑜和诸葛亮各自具有怎样的性格特点?周瑜:_______________________ 诸葛亮:______________________ 5.请发挥你的想象力,诸葛亮在跟周瑜立下军令状之前,想过些什么?___________________________________________________________ ___________________________________________________________(二)军神手术台上,一向从容镇定的淡克医生,这次双手却有些颤抖,他额上汗珠滚滚,护士帮他擦了一次又一次。
小升初数学专项练习一线名师严选内容,逐一攻克☆基本概念、基本原理、基础技能一网打尽☆点拨策略思路,侧重策略指导,拓宽眼界思路☆4.作旋转一定角度后的图形【小升初考点归纳】1.旋转作图步骤:(1)明确题目要求:弄清旋转中心、旋转方向和旋转角;(2)分析所作图形:找出构成图形的关键点;(3)找出关键点的对应点:按一定的方向和角度分别作出各关键点的对应点;(4)作出新图形:顺次连接作出的各点.(5)写出结论:说明作出的图形.2.中心对称作图步骤:(1)连接原图形上的所有特殊点和对称中心;(2)再将以上连线延长找对称点,使得特殊点与对称中心的距离和对称点与对称中心的距离相等;(3)将对称点按原图形的形状顺次连接起来,即可得出关于对称中心对称的图形.【经典例题】一.选择正确的答案,把序号填在括弧中(共1小题)1.(2016•长沙模拟)下面图形中,以某一边为轴旋转一周,可以得到圆锥的是()A.B.C.D.【解析】解:直角三角形沿一条直角边旋转一周得到的几何体是一个圆锥.故选:A.二.操作题(共14小题)2.(2019春•南京月考)(1)将先向下平移5格,再向右平移13格.(2)将平行四边形沿A点顺时针方向旋转90°.【解析】解:(1)将先向下平移5格(下图红色部分),再向右平移13格(下图绿色部分):(2)将平行四边形沿A点顺时针方向旋转90°(下图蓝色部分):3.(2019春•枣阳市校级月考)(1)将图形A绕点O点顺时针旋转90°得到的图形B.(2)将图形B向右平移4格得到图形C.【解析】解:(1)将图形A绕点O点顺时针旋转90°得到的图形B(下图):(2)将图形B向右平移4格得到图形C(下图):4.(2018•泉州)(1)按要求画图.①将图中的三角形①绕O点顺时针旋转90°,画出旋转后的图形②.②将图中的三角形①平移,使平移后的三角形顶点O的位置在(9,5),画出平移后的图形③.【解析】解:根据分析可得,5.(2018春•新罗区期末)画一画:(1)把图形绕点O逆时针旋转90°.(2)把旋转后的图形向下平移两格.【解析】解:6.(2018•漳平市校级模拟)做一做,画一画(1)画出图形A的另一半,使它成为一个以直线a为对称轴的对称图形.(2)画出把图形B向右平移6格后得到的图形.(3)画出把图形C绕O点顺时针旋转90°后得到的图形.(4)用数对表示O点的位置是(8,6).【解析】解:(1)画出图形A的另一半,使它成为一个以直线a为对称轴的对称图形.(2)画出把图形B向右平移6格后得到的图形.(3)画出把图形C绕O点顺时针旋转90°后得到的图形.(4)用数对表示O点的位置是(8,6).故答案为:8,6.7.(2018春•隆化县校级期末)画出三角形AOB绕O点逆时针旋转180o后的图形.【解析】解:画出三角形AOB绕O点逆时针旋转180°后的图形(图中红色部分):8.(2018春•卢龙县期中)画出三角形AOB绕点O逆时针旋转90度的图形.【解析】解:画出三角形AOB绕点O逆时针旋转90度的图形(图中红色部分):9.(2018秋•廉江市期中)画出三角形AOB绕B点顺时针旋转90度后的图形.【解析】解:作图如下:10.(2018•兴仁县)按要求画一画.(1)画出图形A向右平移5格后得到的图形B.(2)画出图形B绕点O逆时针旋转90°后得到的图形C.【解析】解:(1)画出图形A向右平移5格后得到的图形B(下图):(2)画出图形B绕点O逆时针旋转90°后得到的图形C(下图):11.(2017春•海南区期末)画出三角形AOB绕O点顺时针旋转90度后的图形.【解析】解:根据题干分析画图如下:12.(2016春•洛阳月考)将长方形绕A点顺时针旋转90°.【解析】解:将长方形绕A点顺时针旋转90°(图中红色部分):13.(2016春•新郑市校级月考)画出下面的图象中的三角形沿着A点顺时针旋转90度后的图形.【解析】解:三角形沿着A点顺时针旋转90度后的图形(红色部分):14.(2016秋•永州期中)把如图的小三角旗绕点A沿顺时针方向旋转90度.再向右平移4格.分别画出旋转和平移后的图形.【解析】解:画图如下:15.(2016春•南海区期末)画出面积是3平方厘米的三角形AOB并绕O点逆时针旋转180o 后的图形.【解析】解:根据题干分析可得:三.解析题(共7小题)16.(2019春•东海县月考)按要求画一画.①将长方形绕A点逆时针旋转90°.②将小旗围绕B点逆时针旋转90°.【解析】解:作图如下:17.(2019春•古浪县校级期末)先将△ABC绕点C点顺时针旋转90°得到△A′B′C,再将△A′B′C′向下平移4格.【解析】解:先将△ABC绕点C点顺时针旋转90°得到△A′B′C,再将△A′B′C′向下平移4格.18.(2018春•抚宁区期末)画出绕点“O”顺时针旋转90度后的图形.【解析】解:作图如下:19.(2017秋•保定期末)画出三角形逆时针旋转90度后的图形.【解析】解:作图如下:20.(2018春•桃城区校级期末)(1)小鱼图从右下方移至左上方,先向上平移3格,又向左平移5格.(2)把梯形绕A点顺时针方向旋转90°,画出旋转后的图形.【解析】解:(1)根据题干分析可得:小鱼图从右下方移至左上方,先向上平移3格,再向左平移5格;(2)根据分析画图如下:故答案为:上、3、左、5.21.(2017春•绍兴期末)画出三角形AOB绕O点顺时针旋转90°后的图形.【解析】解:画出三角形AOB绕O点顺时针旋转90°后的图形:22.(2017春•绍兴期末)画出三角形AOB绕O点顺时针旋转90°后的图形.【解析】解:画出三角形AOB绕O点顺时针旋转90°后的图形:。
统编版语文四年级下册 暑假字词专项(五)——成语专项一、选择题1. 下面加点的词语使用不恰当的一项是( )A .面对敌人的审问,小雨来从容不迫....地一一回答。
B .我们一起去看望了生病的朱小敬同学,然后扬长而去....。
C .做学问要一丝不苟....,不能有半点儿马虎。
D .这件事我真是无能为力....,你请别人帮忙吧。
2. 下列各句中,加点的词语使用不正确的一项是( )A .我们上课要专心,不可左顾右盼....。
B .从监控上看,小偷偷了东西扬长而去....。
C .突然,狂风大作....,我们只能回到屋子里。
D .王明头脑灵活,做起事来总是三眼..一板..。
3. 下列加点词语使用不当的一项是( )A .他们把桌椅饭菜搬到门前,海阔天空....地吃起来。
B .谈起鸟类,我们头脑中自然会浮现轻灵的鸽子或者五彩斑斓....的孔雀。
C .等到鹅再来吃饭的时候,饭罐已经空空如也....。
D .救援工作进行得井然有序....,几乎没有发生什么争执或殴斗。
4. 下列句子中,加点词语使用不正确的是( )A .我们在沙滩上留下一串串踪迹..B .每逢..下雪,我们就到院子里打雪仗,堆雪人。
C .这篇文章初读觉得平平常常....,过后却回味无穷D .严冬到来,北风呼啸....,大雪漫天飞舞 5. 下列句子中加点的词语运用不恰当的一项是( )A .三岁的妹妹整天无忧无虑....地玩耍。
B .我们正步走时要向前看,不能左顾右盼....。
C .他性格开朗,不怕生人,总是局促不安....地和别人交谈。
D .这个推销员三番五次来我家,我不胜其烦....,就买了他的东西。
6. 下列句子中,加点成语使用最恰当的一项是( )A .当我失败的时候,看着亲人宽慰的眼神,我会惊恐万状....。
B .当我的好朋友遇到烦心事时,我愿意出谋划策....。
C .当我面对陌生人的时候,假如他的目光躲闪阴暗,我会挺身而出....,敬而远之。
统编版语文五年级下册暑假专项练习——阅读理解(五)一、阅读短文《董存瑞舍身炸碉堡》,完成练习。
董存瑞瞪着敌人的碉堡,两眼迸射岀仇恨的火花。
他跑到连长身边,坚决地说:“连长,我去炸掉它!”□连长□我掩护□□战友郅顺义也恳切地说。
连长和指导员商量了一下,同意了他们的请求。
“同志们,扔手榴弹!”连长给战士们下了命令。
董存瑞抱起炸药包,郅顺义背起两兜手榴弹,同时跃岀战壕,冲了上去他们互相配合,郅顺义扔一阵手榴弹,董存瑞就向前跃进几步;郅顺义再扔阵,董存瑞再跃进几步。
跟在后面的战友把一捆捆手榴弹送到郅顺义手里。
敌人的机枪更疯狂了,子弹嗖嗖地打在董存瑞身边,地上冒起了点点尘土和白烟。
董存瑞夹紧炸药包()忽左忽右地匍匐前进,()又向前滚了好几米。
突然,他身子一震,左腿中了一枪。
他用手一摸,全是血。
敌人的机枪一齐向董存瑞扫射,在他面前交织成一道火网。
董存瑞离碉堡只有几十米了。
他隐蔽在一小抉凹地里。
郅顺义接二连三地扔手榴弹掩护。
董存瑞趁着腾起的黑烟,猛冲到桥下。
董存瑞看看四周,这座桥有一人多高,两边是光滑的斜坡。
炸药包放在哪儿呢?他想把炸药包放到河沿上,试了两次,都滑了下来。
要是把炸药包放在河床上,又炸不毁碉堡。
就在这时候,嘹亮的冲锋号响了,惊天动地的喊杀声由远而近。
在这万分紧急的关头,董存瑞昂首挺胸,站在桥底中央,左手托起炸药包,顶住桥底,右手猛地一拉导火索。
导火索“哧哧”地冒着白烟,闪着火花。
火光照亮了他那钢铸一般的脸。
一秒钟、两秒钟……他像巨人一样挺立着,两眼放射着坚毅的光芒。
他抬头眺望远方,用尽力气高喊着:“同志们,为新中国,冲啊!”巨大的喊声震得地动山摇,前进的道路炸开了。
战士们冲过烟雾,沿着董存瑞开辟的道路杀向敌军司令部,消灭了全部敌人。
胜利的红旗在隆化中学上空迎风飘扬。
1.在第1自然段的“□”里填上恰当的标点。
2.在文中的括号里填上合适的关联词语。
3.董存瑞和郅顺义是怎样配合的?________________________________________________________________________________ 4.董存瑞在冲到桥下前遇到了哪些困难?________________________________________________________________________________ 5.董存瑞在安放炸药包时遇到了什么麻烦?他是怎么解决的?________________________________________________________________________________ 6.谈谈你对文中画“”句子的理解。
新人教版小学二年级数学上册计算题专项练习(一)一、口算。
9×5= 76-18= 7×6= 46+32= 48+20= 8×5= 9×8= 43-7=4+4= 8×7= 13-3= 8×3=7×9= 7×5= 8+37= 9×6=8×4= 6+8= 51-3= 8×2=6×9+9= 8×5+37= 8×6-8=40+9×3= 67-6×5= 9+8×9=二、列竖式计算。
47+39= 51-36= 56+34= 73-(26+38)= 36+47-65=新人教版小学二年级数学上册计算题专项练习(二)一、口算。
8×3= 36+8= 9×4= 63-7= 88-45= 8×7= 8×8= 13+17= 4×7= 8+6= 13-3= 8×3=6×9= 7×2= 22+37= 6+6=6×4= 6+8= 51-13= 9×8=3×8+8= 5×7+5= 9×6-6=30+7×6= 67-3×7= 8+8×8=二、列竖式计算。
73-66= 27+49= 89-47=64-(62-35)= 54-26+49=三、把口诀补充完整。
()九五十四六七()八()七十二()八五十六四九()五()三十五()二十八()四十五()三十六四、括号里最大能填几?8×()< 60 42>()×6 27>4×()()×5<36 70> 9×()()×3<22 五、看图写算式。
乘加算式:乘减算式:六、解决问题。
1、二年级一班有36名女生,男生比女生少9人。
2023年小学六年级语文下册专项练习题(五)(一)边城(节选)沈从文边城所在一年中最热闹的日子,是端午,中秋和过年。
三个节日过去三五十年前如何兴(xīng xìng)奋了这地方人,直到现在,还毫无什么变化,仍能成为那地方居民最有意义的几个日子。
端午日,当地妇女小孩子,莫不穿了新衣,额角上用雄黄蘸酒画了个王字。
任何人家到了这天必可以吃鱼吃肉。
大约上午十一点钟左右,全茶峒人就吃了午饭,把饭吃过后,在城里住家的,莫不倒(dào dǎo)锁了门,全家出城到河边看划(huáhuà)船。
河街有熟人的,可到河街吊脚楼门口边看,不然就站在税关门口与各个码头上看。
河中龙船以长潭某处作起点,税关前作终点。
作比赛竞争。
因为这一天军官税官以及当地有身分的人,莫不在税关前看热闹。
划船的事各人在数天以前就早有了准备,分组分帮各自选出了若干身体结实手脚伶俐的小伙子,在潭中练习进退。
船只的形式,与平常木船大不相同,形体一律又长又狭,两头高高翘起,船身绘着朱红颜色长线,平常时节多搁在河边干燥洞穴里,要用它时,拖下水去。
每只船可坐十二个到十八个桨手,一个带头的,一个鼓手,一个锣手。
桨手每人持一支短桨,随了鼓声缓促为节拍,把船向前划去。
坐在船头上,头上缠裹着红布包头,手上拿两支小令旗,左右挥动,指挥船只的进退。
擂鼓打锣的,多坐在船只的中部,船一划动便即刻蓬蓬镗镗把锣鼓很单纯的敲打起来,为划桨水手调理下桨节拍。
一船快慢不得不靠鼓声,每当两船竞赛到剧烈时,鼓声如雷鸣,加上两岸人呐喊助威,便使人想起梁红玉老鹳河时水战擂鼓,牛皋水擒杨幺时也是水战擂鼓。
凡把船划到前面一点的,必可在税关前领赏,一匹红,一块小银牌,不拘缠挂到船上某一个人头上去,皆显出这一船合作的光荣。
好(hǎo hào)事的军人,且当每次某一只船胜利时,必在水边放些表示胜利庆祝的五百响鞭炮。
1.用“\”画去文中多音字不恰当的读音。
小学三年级阅读理解专项练习题(5、6)阅读理解(五)______________________一根纤细的火柴被主人划着,火苗欢舞着,yi chang()兴奋。
远处的风看见火柴纤弱的生命,在顷刻间即将灰飞烟灭,感到十分惋(wan)惜,便急速跑过去,一口气吹灭了ran shao()的火苗,救了火柴。
熄灭了的火柴被主人扔在地下。
火柴抬头对风说:“风婆婆,你怎么吹灭了我呀!”风回答孩子我是不忍心看着你短暂的生命那么快就完结了啊火柴听后,叹息道:“唉,风婆婆,我短暂的生命最大的价值就在于燃烧啊!可您扼杀了我短暂(zan)的生命中的闪光点……”1.给短文加个题目_________________(3分)2.在()里填上正确的词语。
3.联系上下文,解释下列词语(4分)惋惜:灰飞烟灭:4.给第四自然段加上标点(3分)5.火柴的闪光点是_______________。
短文反映了火柴什么样的品质?()(3分)(1)好出风头,想炫耀自己。
(2)忘恩负义,别人救了它,还不领情。
(3)有牺牲精神,为了照亮别人,不惜毁灭自己。
(4)不明事理,不辨是非,不识好人心。
6.你知道生活中有哪些像火柴这样的人或物吗?(3分)7.风婆婆为火柴即将被烧掉而感到惋惜,把火柴吹灭了,你觉得对不对?为什么?(4分)阅读理解(六)酷夏六月十五那天,天热得发了狂。
太阳刚一出来,地上已经像着了火。
一些似云非云似雾非雾的灰气低低地浮在空中,使人觉得憋气。
一点风也没有。
街上的柳树像得了病似的。
叶子挂着层灰土();枝条一动也懒得动,()地低垂着。
马路上一个水点也没有,()地发着白光。
便道上尘土飞起很高,跟天上的灰气联结起来,结成一片毒恶的灰沙阵,烫着行人的脸。
处处干燥,处处烫手,处处憋闷,整个老城像烧透了的砖窑,使人喘不过气来。
狗趴在地上(),骡子的(),柏油路仿佛要晒化了,一切显得那么寂静。
1.选择下列词句填在文中括号里。
(3分)鼻孔张得特别大干巴巴吐着红舌头无精打采在枝上打着卷儿2.联系上下文解词(3分)憋闷:寂静:3.全文共有()个自然段,标出序号。
第五单元复习专项——阅读理解题班级:_________ 姓名:__________一、现代文阅读车把上的纸鹤①一年暑假,我独自一人去江南一座古城旅游。
古城的景点很多,但都分散在各处。
我这个穷学生只能从一家车行里租一辆七成新的自行车,骑车浏览古城。
②第三天下午,我骑车来到郊外的一个著名风景区,环顾四周,没有找到寄存自行车的地方,只看见公园对面那片小树林里,横七竖八地放着几辆自行车。
于是,我便将自行车也往那里一放,返身兴致勃勃地买票进了公园。
③当我坐上了驶往湖心岛的游船时,猛地想起自行车好像忘了上锁,一摸口袋,果然不见有车钥匙。
我顿时惊出一身大汗,心想:!苦苦哀求船工将我放上岸去。
船尚未停稳,我就像箭一般地蹿上岸,拼命朝公园出口处跑。
④出了公园大门,我远远地朝对面那片林子望去,不好,那里只剩下孤零零的一辆自行车了。
我的心狂跳不已,跑过去一看,啊!不禁喜出望外,正是我租来的那辆车呢!可是车是锁着的,仔细一看,车把的刹车上夹着一只用纸做的鹤。
我的心头涌上一阵希望:那车钥匙会不会就在纸鹤里呢?取下纸鹤,一摸,硬硬的,它的肚子里果然藏着一把钥匙!⑤我端详着这只可爱的纸鹤,竟然发现它的尾部还歪歪扭扭地写着几个字:“叔叔,请小心!”激动的暖流顿时传遍全身……⑥如今,这纸鹤已成为我的珍藏,它珍藏着那位好心孩子对我的一份关爱,也珍藏着我对他的一份怀念。
1.“顾”字在字典中的解释有:①回头看,泛指看;②拜访;③照管,注意。
“环顾四周”中“顾”的意思是______。
(填序号)2.联系上下文,在文中横线处将“我”的心理活动写下来。
3.梳理故事内容,完成表格。
4.根据文中叙述的内容,给下列反映作者感情变化的词语排序。
(填序号)①喜出望外②兴致勃勃③激动不已④心急如焚正确的顺序是:________________。
5.把车钥匙放在纸鹤里有什么好处?下列说法正确的一项是()A.既安全收藏了钥匙,又装饰了单调的自行车B.车主人能够心领神会,而别人不会轻易发现C.跟车主人闹着玩儿,给对方一个惊喜6.看到纸鹤,“我”为什么会“激动的暖流顿时传遍全身”?___________________________________________________________________________________二、阅读理解。
一、小数的巧算(一)填空题1. 计算 1.996+19.97+199.8=_____。
2. 计算 1.1+3.3+5.5+7.7+9.9+11.11+13.13+15.15+17.17+19.19=_____。
3. 计算 2.89⨯4.68+4.68⨯6.11+4.68=_____。
4. 计算 17.48⨯37-17.48⨯19+17.48⨯82=_____。
5. 计算 1.25⨯0.32⨯2.5=_____。
6. 计算 75⨯4.7+15.9⨯25=_____。
7. 计算 28.67⨯67+3.2⨯286.7+573.4⨯0.05=____。
(二)解答题8. 计算 172.4⨯6.2+2724⨯0.38。
9. 。
10.计算 12.34+23.45+34.56+45.67+56.78+67.89+78.91+89.12+91.23。
二、数的整除性(一)填空题1. 四位数“3AA1”是9的倍数,那么A=_____。
2. 在“25□79这个数的□内填上一个数字,使这个数能被11整除,方格内应填_____。
3. 能同时被2、3、5整除的最大三位数是_____。
4. 能同时被2、5、7整除的最大五位数是_____。
5. 1至100以内所有不能被3整除的数的和是_____。
6. 所有能被3整除的两位数的和是______。
7. 已知一个五位数□691□能被55整除,所有符合题意的五位数是_____。
(二)解答题8. 173□是个四位数字,数学老师说:“我在这个□中先后填入3个数字,所得到的3个四位数,依次可被9、11、6整除。
”问:数学老师先后填入的3个数字的和是多少?9.在1992后面补上三个数字,组成一个七位数,使它们分别能被2、3、5、11整除,这个七位数最小值是多少?10.在“改革”村的黑市上,人们只要有心,总是可以把两张任意的食品票换成3张其他票券,也可以反过来交换。
试问,合作社成员瓦夏能否将100张黄油票换成100肠票,并且在整个交换过程中刚好出手了1991张票券?三 质数与合数(一)填空题1. 在一位的自然数中,既是奇数又是合数的有_____;既不是合数又不是质数的有_____;既是偶数又是质数的有_____。
上海高考英语口语考试专项练习(五)上海高中教研教学听短文回答问题测量目标:能根据所听材料回答问题。
答题提示:此题考查在听懂短文的基础上口头回答问题。
要注意,题目要求中的那句话很重要,是对短文主要内容的概括,对于听懂短文内容有很大帮助。
针对每篇短文所提的两个问题会在屏幕上显示出来,所以看着问题听短文会帮助学生理解文章内容。
第一个问题通常是对文中某个或某些具体信息提问,可以边听边对所需信息做些简单的记录,以便答题时用。
第二个问题通常针对与短文重点有关的内容发表个人的看法和见解,.并对自己的观点和看法给予简单的论证。
每个人可以根据自己的经历和见识,合理恰当地利用短文中的信息,组织好语言,清楚说出自己的见解。
Directions: In this section, you will hear a short passage. The passage will be read twice. After you hear the passage, answer the first question with the information you hear and the second in your own opinion with at least 3 sentences. For the first-questions you will have 30 seconds to prepare and 30 seconds to talk. For the second question, you will have one minute to prepare and another minute to talk.Passage 1Questions:1.What are the two reasons that the speaker mentioned for his dropping out of his college?,2.Do you think university education is meaningful to your life? Why or why not?Passage 2Questions:1.What are the needs the family want the tourist officer to meet in their travel arrangement? List at least 3 needs.2.Would you like*to travel as part of a tour group or travel independently?Passage 3Questions:1.What does the American education mainly emphasize on?2. Are you a study machine? why or why not?Passage 4Questions:1.Can you list four features of Canadian National Tower in Toronto?2.If you were asked to choose one place in Shanghai for a visit, which one would you choose? Why?Passage 5Questions:1.What are the two changes regarding the school security?2.If you could suggest one change which should be done in your school, what would it be?Passage 6Questions:1. How many examples of the word service are mentioned in the passage?2.What kind of service would you expect in a restaurant?Passage 71. From which countries do the tourists behave worst at hotels according to the survey?2. What do you think a person should do to be a good tourist while visiting other countries?Passage 8Questions :1. What kinds of business did the island of Bellonia have before the discovery of oil?2. What would you want to know most if your company is going to have a meeting with the team from the Bank of Belllonia?Passage 9Questions:1. What are the three pieces of luck the girl has in the passage ?2. What do you think one needs to become successful from nothing ?Passage 10Questions:1.Why did Max write a marvelous description of his teacher?2.What do you thirdly should be done if students can evaluate their teachers more objectively?Passage 11Questions1. List the water sports that Jason is going to choose in this year’s competition.2. What is your favorite sport activity? Explain why you like it.Passage 12Questions:1.Why will Tina choose a glass vase as a present for her mother's birthday?2.Of all the presents you have received, what is your favorite? Why?Passage 13Questions:1. What are the facilities inside Jimmy’s apartment?2. If you travel abroad,will you exchange your home with a family like Jimmy’s? Why or why not?Passage 14Questions:1. What are three problems the computerized system solves in this Japanese supermarket?2. What do you think is the biggest problem a supermarket should solve in your city ? Why?Passage 15Questions:1. Why are some breakfast cereals especially attractive to children according to the passage ?2. Do you like your breakfast? Why or why not?Passage 1Listen to the following speaker talking about his college education.At the age of 17,1 went to college. But I naively chose a college that was almost as expensive as Stanford, and all of my working-class parents' savings were being spent on my college tuition. After six months , I couldn't see the value in it . I had no idea what I wanted to do with my life and no idea how college was going to help me figure it out. And here I was spending all of the money my parents had saved in their entire life. So I decided to drop out and trust that it would all work out OK. It was pretty scary at the time, but looking back it was one of the best decisions I ever made. The minute I dropped out I could stop taking the required classes that didn't interest me, and begin dropping in on the ones that looked interesting.Passage 2Listen to the following speaker talking about Margaret's family travel plan.Margaret's family has won a holiday to Saipan. Margaret's father is a businessman and is often away from home. Since he usually spends so much time rushing from place to piece, he would like a relaxing, holiday with as much swimming as possible. Her mother works five days in a hospital. She prefers to be more active on holiday and loves walking and playing games on the beach. Margaret and her brother Kevin would like to meet some people of a similar age and think that the best way to do this is to go to disco in the evening. The children are happy with their father's choice of hotel. They don't like to eat in local restaurants and would prefer to eat at the hotel. The family has sent their needs to the Saipan Tourist Office. It offers a free service to holiday-makers who want to visit the island.Passage 3Listen to the following speaker talking about American education.In the United States we emphasize a lot on building a person's leadership, organizational skills , and just everything as a whole . You are not just a study machine . You are someone who needs to develop your talent. If you have any inner talent, they want to just get it out, you know. So if they see potential in you in sports, they will ask you to join a sports team. A lot of people get scholarship because they are excellent in football, or basketball or baseball. They can get scholarship for that, for their college education. And if you are a good leader you can join or start a student club and become the president of the student club, so that's ... And also for many schools it's one of the requirements for students to do community service, meaning to volunteer for businesses, or non-profit organizations, and stuff like that. They must do that in order to earn enough points, and if s one of the requirements for them to graduate.Passage 4Listen to the following speaker talking about Canadian National Tower.If you come to Toronto, Canadian National Tower is a place you must see, taste and experience. Tourists can take glass-faced lifts outside the tower up to the Sky Pod viewing platform at 340 meters. Then it's another 100 meters up to the Observation Decks. There you can see Toronto with a 360 degree viewing, and see as far as Niagara Fall, New York State and more. Tourists can enjoy a fine dinner at world’s highest revolving restaurant, or have a drink at the world ‘s highest bar called Horizon Bar. It seems to me the biggest attraction is the Glass Floor. It is 113 storeys above the ground! Walking on it is like as if you were walking on air. You can do it if you dare! Take another lift from Observation Decks and go up an additional 33 storeys to the Space Deck. It's the world's highest observation gallery. There you can see an even more spectacular view of Toronto.Passage 5Listen to the following speaker talking about security changes being made on his school campus.In the past few weeks, a couple of big changes regarding the school security have taken place. The biggest change is making everyone show ID to enter the campus. Whenever you enter the school, you must have your ID card out and present it to the guard. Guests must make an appointment ahead of time in order to enter the school You may also have noticed that you cannot get back on campus after 6:00 p.m. Some of you leave your bags in your desks while you go off campus to get food or play sports, and then discover you cannot get back inside. Entry after 6:00 p.m. will not be allowed unless you are part of a school event It means you must leave school by 6:00 p.m. I want to emphasize that you need to take note of your surroundings and any unfamiliar people to ensure a safe campus for everyone.Passage 6Listen to the following speaker talking about the service in Britain.I read in the newspapers that Britain has the biggest service industry in Europe: I have-never seen it: This-is strange because “service” is a word we use a lot in English. Most hotels have terrible room service. It's impossible to get a meal in your room after nine o’clock Banks promise a high level of customer service if there’re advertisements, but when I go to the bank there are only two bank clerks available. Of course, at lunch time when lots of people need to go to the banks it's different. Then there’s only one clerk! And in most shops it’s hard to find “service with a smile”.Last week at the Sasasara Restaurant in Wellington Road, I had my worst ever experience of service in this country! My main course took one hour to arrive at the table. Looking at the food made me feel ill and I suffered three days of food poisoning after I ate it. I have recovered now but I don’t plan to go back for dessert!Passage 7Listen to the following speaker talking about a recent survey online.A recent survey by an online travel agency found that British people were the worst at speaking a foreign language while the Germans were the best. The French were second. The British, Americans and Indians were also the worst at trying local food and adapting to local ideas and customs. Best were the Italians, Spanish and Germans.…The survey also asked hotel staff to comment on the behavior and politeness of different nationalities. Once again, the Germans were seen as the most polite. Americans, Japanese and Italians came second. Tourists from Ireland, Denmark and Britain were the worst.This not to say that the Germans were the best at everything, however! When it comes to giving tips the United States came out on top, with Japan a close second. Germans were a long way down the list. Interestingly, Germans were also seen as unfriendly to foreigners in their own country.Listen to the following speaker talking about the island of Bellonia.Two years ago, nobody had heard of the island of Bellonia. This beautiful island with a population of 500,000 people had some hotels, sugar plantation, a small fishing industry and not much else. But everything changed with the discovery of oil. Lots of oil! So much, that this tiny country is now making more money than Saudi Arabia! The Bellonia government is looking for ways to make sure that when the oil is eventually gone, the country stays rich.According to my information a team from the Bank of Beilonia is currently visiting European companies, looking for suitable business partners for many kinds of government projects. The areas include tourism, technology, education, banking, telecommunications and so on. The plain is to invest at least 5 billion over the next five years. Any company which can start business with Bellonia now has a very good chance of making a lot of money over the next twenty years.Passage 9Listen to the following speaker talking about a story of an African girl.I was a girl born in the deserts of Sornaliarb When I was about T3 my father said to me, I've found you a husband! We have arranged that he will give me five camels." That night I ran away. For almost three weeks, I walked through the desert, but finally I got to my auntie's house. Auntie's husband was an ambassador and in a few months I flew to Britain to work at his London house.One day, a photographer called Michael Goss saw me in the street. He took my picture and the photographs were beautiful. 'You should try and do modeling", he told me. Then one day I took these photographs to an agency. They sent me to a studio, and my picture appeared on the cover of _a .calendar. Soon after that, the agency got me a part in the James Bond film The Living Daylights.That was seven years ago. Since then I've done modeling all over the world and I've appeared in magazines such as V ogue and Elle. Once I was worth five camels. Now I can earn up to £5,000 for one day's work. I've gone from the bottom to the top.Passage 10Listen to the following speaker talking about the evaluation of teachers.Every Semester we are given the opportunity to evaluate our teachers. We are supposed to judge their lectures, interest in student problems, methods of assigning work, and general ability to conduct a class.It is very, difficult to evaluate another person's performance objectively. For example, Viviane recently wrote irresponsible remarks about her teacher because she was failing the course. Her friend Max wrote a marvelous description of the same teacher because he was receiving an A in the course. Both Viviane and Max were not fairly evaluating the teacher. They were influenced by the grades they were earning and were misled in their judgment.Viviane and Max have not thought about their teacher's teaching abilities. They have written unfair evaluations and have not given thought to their ratings. They have not made fair judgments, but instead have been influenced by personality and have considered little work with excellence in teaching.Passage 11Listen to the following speaker talking about Jason’s favorite sports.Since early childhood, Jason has loved practicing every kind of water sports. As he lives in Saipan, he has easy access to shallow water on the beaches and to deep water in the sea. By now he is an expert swimmer and diver. He is also good at rowing, sailing and water skiing. Moreover, his favorite activity is windsurfing. In 2010, Jason took part in the Sea Water Sports Competition and won a bronze medal, coming third in the deep-seaThe Sea Water Sports Competition will be held in October this year again and Jason is going to choose diving, swimming and sailing, but he has no doubt that his best chance of a medal this time will be in windsurfing. If he is successful in this competition Jason plans to try for a scholarship to a college, where he can be trained as a water sports instructor. After that he would be able to have a job teaching a variety of activities on rivers , lakes or oceans.Passage 12Listen to the following speaker talking about Tina's choice of a present for her mother..Tina currently lives in Auckland, New Zealand. It's her mother's birthday in two weeks' time and she has to buy a present for her mother. The big problem is that her mother lives in Australia, and Tina will not be able to give it to her personally. She has decided to select a suitable present from the catalogue of a company called Delightful Home. This company specializes in delivering to different countries. Tina has used this company before and found the service excellent.Her mother, Barbara, lives in a house with a big garden. She has a passion for growing plants. At most time of the year, the house is filled with the scent from the flowers she has picked from the garden. She needs vases for all these flowers, so Tina has decided to buy a nice glass vase from the catalogue. Tina wants the present to be delivered directly to her mother's address. Tina thinks this will be a nice surprise to Barbara.Passage 13Listen to the following speaker talking about Jimmy's idea of exchanging apartment for holiday.Jimmy and his family have a small apartment in Warsaw, Poland. They would like to exchange their apartment for holiday with people from other countries. The apartment is situated on the second floor of a block near the city center. The transport facilities to get from their home to the shops are good with many bus services. It's possible to walk to the city center.The apartment has two bedrooms, a kitchen and a sitting room. It's possible for four people to sleep in the apartment. There are machines for washing and drying clothes, and a telephone, a computer and an access to the internet.The area has facilities for leisure activities within walking distance: a cinema and a large supermarket nearby, a small swimming pool to the east and a national park to the west.When the exchange family arrives, they can pick up the key to the apartment from local agency next to the apartment block. Exchange families can contact the agency by email at exchangehome@.Passage 14Listen to the following speaker talking about a Japanese supermarket.One supermarket in Tokyo has managed to solve the problems of shoplifting, mistakes by cashiers, and long lines of customers waiting at cash registers. It is Japan's advanced computer technology that has come up with the answer.Shoppers at an OK supermarket of the City now push a cart with a plastic card chained to it and buy from glass cases where the goods are on display. The plastic card has a magnetic number imprinted on While shopping, the customer pushes the card into a slot beside whichever items are wanted and push a button or two. The glass-covered machines are connected to a computer that knows the price of every item in the store. Prices of every purchase are added up automatically. When she has finished shopping, the customer hands her card to a cashier who feeds it to the register. A second later the total pops out.Shoplifting is physically impossible.. Once you touch a commodity, the computer remembers it no matter how you hide it or even if you eat it on the spot.A cashier at the OK supermarket is now able to work 15 times faster than her colleague at a conventional supermarket. Only two cashiers, for instance, are required at the store, which sells 2,500 separate items.Passage 15Listen to the following speaker talking about different breakfasts.Different people eat different foods, especially for breakfast. Atypical Japanese breakfast, for example, includes various kinds of seaweed and either raw or cooked fish in different sauces. Most Chinese like to begin the day with a bowl of thin rice soup or a similar dish called congee. The Swiss invented a breakfast called muesli,: which is a mixture of different grains and dried fruits. Nowadays muesli can be bought already mixed, but many people like to buy the separate ingredients and mix their own muesli according to their tastes.For most American families, however, and increasingly throughout the Western world, manufactured and packaged breakfast cereals are gaining in popularity. Western supermarkets sell a wide variety of breakfast cereals. They often contain a lot of sugar and many of them have fun names and sometimes include little toys,which make them especially attractive., to children. Most of these cereals are crushed and then cooked under pressure until it is light and crunchy. It is usually eaten with milk, and most people also add fruit or sugar.Passage 11.The college was so expensive arid his working class parents couldn't offer to pay his education. He couldn't see the value in college education.2. A lot of examples show that college education will be meaningful to my life because having special knowledge will help me to make my dream come true. I want to be a doctor, so I must have a higher education. Most successful people are well educated. Only few people, like Jobs and Gates, can be successful without a higher education background.Passage 21.They want a hotel with a swimming pool. Children want to go to disco in the evening . Mother prefers to walk and play games on the beach.2.I prefer travelling independently. The process of making my own travel plan is exciting since I have to read a lot about the place I am going to visit. Most of the time during the visit, I can have my own choice of sightseeing and eat what I like.Passage 31.Building a person's leadership, organizational skills and just everything as a whole.2.I am like a study machine. There are too many assignments for me to complete everyday. I don't have time for any non-school reading for my own pleasure. The competition for a good university is giving the pressure. I wish the academic scores should not be the only requirement for university selection.Passage 41.You can enjoy a meal and a drink at the world's highest restaurant and bar there. The glass floor is thrilling to walk on. Up on the decks, you can see the whole Toronto and even as far as Niagara fall and New York. The glass-faced lift's riding is also thrilling.2.I would like to recommend Yu Garden, a famous classical garden built during the Ming Dynasty. It is alandmark of Shanghai. The shopping mall there sells a variety of goods and we can always find attractive traditional handicrafts and tourists souvenirs. If you like local food, you can tiny one of the restaurants, where local special Shanghai food is provided.Passage 51. Whenever students enter the school, they must show their ID card to the guard; students must leave school by 6:00 p.m. and are not allowed to enter the school after 6:00 p.m.2. I would suggest that we should start our morning dasses at 9:00 a.m. instead of 8:00 a.m.. Starting our school day an hour late will have quite a few benefits. a The biggest one is that we can have one more hour's sleep so that we will be more energetic in school learning. We can also have adequate time to enjoy our breakfast. Some of us even can do exercises in the morning.Passage 61.There are 4,2I think the service we expect in a restaurant usually includes delicious food, comfortable surroundings and helpful waiters. The cooking of expert chefs is the main attraction of a restaurant. In restaurants people would like to enjoy some dishes-they can't-cook by themselves. Besides, clean and comfortable surroundings in restaurants are very important. Comfortable surroundings will provide people with a good place to relax. Finally, well-trained and waitresses are absolutely essential. They can do a good service for the customers.Passage 71.From Ireland, Denmark and Britain.2.First, I think, he should respect the local customs. For example, giving tips when necessary according to the local customs. Second, being polite is always very important, such as talking with people friendly and speaking quietly in public places. No smoking is also the rule that should be observed.Passage 81.Some hotels, sugar plantation and a small fishing industry.2.I think the following important information should be got to know dearly: What kind of project is Bellonia interested in? When are they thinking of starting these projects? How much money has the bank got to invest in the projects?Passage 91.Her auntie's help, meeting with the photographer and the agency's value of her photos.2.I think one's personal will and strong determination are the most important. They made the girl in the story walk through the desert for three days. Then, good luck is necessary. Her auntie, the photographer and the agency are all her luck fairies. Without their help, she would be nothing.Passage 101.Because he got an A in the course the teacher taught.2.Before they do their evaluation, students should be given some guidance. It includes why they should evaluate teachers, what the evaluation standards are, and how they rate the teaching, etc. These instructions can help them to give a more objective and fair evaluation and avoid something irresponsible.Passage 111.Swimming, diving, sailing and windsurfing.2.My favorite sport activity is jogging. Unlike s6me of the sport activities, jogging doesn't need any equipment, except a pair of comfortable running shoes. I can do jogging along the street, on the playground or in the gym. I can do it alone or in a group with my friends, or even with my dog. Jogging is not only a lot of fun, but it also makes me healthy and dynamic.Passage 121. Her mother loves growing flowers in her garden and needs vases for the flowers to put in her house.2:My favorite gift is a music box. I got it as a birthday present at the age of eight from my grandma. When I opened it, the music Happy Birthday played and a little plastic pink girl danced gracefully on the box. Grandma_knew I loved dancing and music. It once gave me a lot of imaginations. I still keep the music box because it reminds me of my grandma's love and thoughtfulness.Passage 131.Machines for washing and drying clothes, a telephone, a computer and an access to the internet.2.I won't exchange my home with a foreigner's family because we definitely have a different life style. I "won't feel comfortable if strangers stay in my bedroom or if I live in other's bedroom since at least we have different body smell. My family will prefer to stay in a hotel so that the room service can do everything for us. Holiday is for relaxing and a change. Stay in a stranger's home is a continuation of your daily life at home, but under more pressure.Passage 141.Shoplifting, mistakes by cashiers and long lines of customers waiting at cash registers.2.I think it is the long lines of customers waiting at cash registers. If you go to some supermarkets at the weekend, things will be worse.. Half an hour’s waiting is an routine. People would like to buy things they need during a week, so every cart is full of food and daily necessities. It takes about five to ten minutes for a customer to pay for his goods. Some cashiers are not skilled at their work. That's another reason for the long lines problem.Passage 151.They often contain a lot of sugar and have fun names and sometimes include little toys.2.Not really. Every morning my breakfast is always the same: some bread and a cup of milk. Mother gets up at six in the morning and I get up about half an hour later. Since ifs quite a long way to go to school, we leave home at seven. There is no time to prepare and enjoy a hearty breakfast. Though I don't like my breakfast, it can at least provide the basic nutrition I need.。
专项练习(五)[密度的计算]专 题 概 述在解答各种密度计算题时,我们会发现,只要仔细研究一下各个物理量之间的关系,找出其中一直没有变化的物理量,并通过这个不变的物理量,利用密度的表达式ρ=m V 或推导式m =ρV 、V =m ρ即可解决问题。
►类型一 同种物质 密度相同1.油罐容积为50 m3的运油车装满石油。
从油罐内取样30 mL ,称得其质量为25.5 g ,那么石油的密度是________g/cm3,该运油车共装石油________t 。
2.一块矩形大理石块,人们估测出它的体积为V ,从它上边取下体积为ΔV 的一小块,测得这一小块的质量为Δm ,那么大理石块的密度为________,大理石块的质量为________。
3.明明星期天到亳州南湖去游玩,站在湖边的他突然想到:这么大的湖能容纳多少吨水呢?为此,他进行了以下活动:A 、他从公园管理处得知:湖占地约230亩,蓄水量达50万立方米。
B 、为了获得较准确的数字,他又用标有〝净含量550 mL 〞字样的饮料瓶装满湖水,并用家里的电子秤测出这瓶湖水的质量为0.6 kg ,瓶子的质量为0.03 kg 。
(1)亳州南湖湖水的密度约为多少千克每立方米?(结果用科学记数保留两位小数)(2)亳州南湖湖水的总质量约为多少吨?►类型二 不同物质 体积相同4.一个瓶子装满水时的总质量是400 g ,装满酒精时的总质量是350 g 。
那么瓶子的容积是(ρ水=1.0 g/cm3,ρ酒精=0.8 g/cm3)( )A 、400 cm3B 、250 cm3C 、350 cm3D 、200 cm35.现在树脂镜片广泛取代了玻璃镜片,某种树脂镜片的密度为1.3 g/ cm3,玻璃的密度为2.5×103 kg/m3,每只眼镜片的体积约为4×10-6 m 3,那么用树脂镜片代替玻璃镜片后,一副眼镜质量可以减少约________g。
6.目前世界上已研发出硬度相当于钢铁2~5倍的聚丙烯塑料,某型号汽车的外壳使用的是质量高达237 kg的钢质材料,假设替换成等体积的聚丙烯塑料材质,那么汽车外壳的质量是多少?(钢的密度ρ钢=7.9×103 kg/m3,聚丙烯塑料的密度ρ塑=1.1×103 kg/m3)►类型三不同物质质量相同7.质量相等的水、硫酸、酒精(知ρ硫酸>ρ水>ρ酒精),分别装在规格相同的A、B、C三个试管中,如图Z-5-1所示,那么可判断出( )图Z-5-1A、A中装的是酒精B、A中装的是硫酸C、B中装的是酒精D、C中装的是水8.在调好的天平两盘上各放一铝块和铁块,天平恰能保持平衡,那么铝块与铁块的质量之比为________,体积之比为________。
(铁的密度为7.9 g/cm3,铝的密度为2.7 g/cm3)9.细心的小明发现寒冷的冬天放在室外的盛水缸常常被冻裂。
是什么原因呢?请你帮他计算:一个容积为0.18 m3的水缸盛满水。
求:(1)水的质量是多少。
(2)水全部结成冰后,冰的质量是多少。
(3)水全部结成冰后,冰的体积是多少。
(ρ冰=0.9×103 kg/m3)►类型四空心类问题10.由同种材料组成的A、B两金属球的质量分别为81 g、50 g,体积分别为30 cm3、25 cm3,假设其中有一个金属球是实心的,那么以下判断正确的选项是()A、A金属球一定是空心的B、B金属球一定是实心的C、该材料的密度可能为2 g/cm3D、该材料的密度一定为2.7 g/cm311.一个铜球体积是30 cm3,质量是178 g,它是空心的还是实心的?假设为空心,那么空心部分的体积是多大?假设往空心部分注入水银,注入水银的质量为多少克?(ρ铜=8.9×103 kg/m3,ρ水银=13.6×103 kg /m3)12.为节能减排,建筑上普遍采用空心砖替代实心砖,如图Z-5-2所示。
空心砖的密度是3×103 kg/m3,每块空心砖的质量是3.6 kg,体积是3000 cm3。
求:(1)每块空心砖空心部分的体积。
(2)生产每块空心砖比同规格的实心砖可节省材料多少千克?图Z-5-2►类型五混合类问题13.八年级某物理研究小组在探究太湖湖水泥沙含量的研究中了解到,单位体积的太湖湖水中含有泥沙的质量,叫做太湖湖水的含沙量,用字母A 表示。
(1)请写出太湖湖水的含沙量的表达式:__________________________。
(2)研究小组成员在一个量筒里放入50 g干燥的〝黄土〞,倒入250 mL清水后,测得总体积为270 mL,由此得到了〝黄土〞的密度,〝黄土〞密度为________。
(3)研究小组成员猜想,含沙量与水和黄土的密度可能有一定的关系。
经过推理,这个关系是成立的。
设水的密度为ρ水,〝黄土〞的密度为ρ土,含沙量为A的湖水密度为ρ,那么用ρ水、ρ土、ρ可以表达出含沙量A,A=_____________________________________________________ ___________________。
14.〝永新家烧〞是永新人民自己酿造的一种白酒,其主要成分是酒精和水。
而酒液的度数是指每100 mL酒液中所含酒精的毫升数,白酒不同的度数都是用蒸馏出来的酒液勾兑而成,酒精的密度为0.8 g/cm3,水的密度为1 g/cm3,求:(1)60度〝永新家烧〞的密度。
(2)如果用60度的家烧假设干勾兑成42度,1000 mL 的酒液,需要60度家烧多少毫升。
详解详析[密度的计算]1.0.85 42.5 2.Δm ΔV Δm ΔV V [解析] 小块大理石的密度:ρ=Δm ΔV, 因为密度是物质本身的一种特性,其大小与质量、体积无关,所以整个大理石块的密度也是Δm ΔV ;整块大理石块的质量:m =ρV =Δm ΔVV 。
3.(1)饮料瓶装满湖水时,水的体积:V1=550 mL =550 cm3,瓶子内湖水的质量:m1=0.6 kg -0.03 kg =0.57 kg =570 g ,湖水的密度:ρ=m1V1=570 g 550 cm3=1.04×103 kg/m3。
(2)湖水的总体积:V =50×104 m3=5×105 m3,湖水的总质量:m =ρV =1.04×103 kg/m3×5×105m3=5.2×108 kg =5.2×105 t 。
4.B [解析] 设瓶子的质量是m ,瓶子的容积是V 。
那么m 水=m1-m ,m 酒精=m2-m ,由于液体的体积等于瓶子的容积,由ρ=m V ,可知m =ρV ,所以,ρ水V =m1-m ,即m +1.0 g/cm3×V =400 g ①,ρ酒精V =m2-m ,即m +0.8 g/cm3×V =350 g ②,解得m =150 g ,V =250 cm3。
5.9.6 6.由ρ=m V 可得,外壳的体积:V =m 钢ρ钢=237 kg 7.9×103 kg/m3=0.03 m3, 那么用聚丙烯塑料做外壳的质量:m 塑=ρ塑V =1.1×103 kg/m3×0.03 m3=33 kg 。
7.A8.1∶1 79∶279.(1)水缸盛满水时水的体积:V 水=0.18 m3,水的质量:m 水=ρ水V 水=1.0×103 kg/m3×0.18 m3=180 kg 。
(2)因质量是物体本身的一种属性,与物体的状态无关,所以,水全部结成冰后,冰的质量m 冰=m 水=180 kg 。
(3)水全部结成冰后,冰的体积:V 冰=m 冰ρ冰=180 kg 0.9×103 kg/m3=0.2 m3。
10.D 11.(1)假设球为实心,其体积应为V 铜=m 铜球ρ铜=178 g 8.9 g/cm3=20 cm3<30 cm3,所以此球为空心的。
(2)空心部分的体积为V 空=V 铜球-V 铜=30 cm3-20 cm3=10 cm 3。
(3)注入水银的体积为V 水银=V 空=10 cm3,由ρ=m V 可得,注入水银的质量为m 水银=ρ水银V 水银=13.6 g/cm3×10 cm3=136 g 。
12.(1)实心部分的体积:V =m ρ= 3.6 kg 3×103 kg/m3=1.2×10-3m3; 每块空心砖空心部分的体积:V 空=3×10-3m3-1.2×10-3m3=1.8×10-3m3。
(2)每块空心砖比同规格的实心砖可节省材料的质量:m ′=ρV 空=3×103 kg/m3×1.8×10-3 m3=5.4 kg 。
13.[导学号:47732245](1)A =m V(2)2.5 g/cm3 (3)ρ土〔ρ-ρ水〕ρ土-ρ水[解析] (1)因为河水的含沙量是指单位体积的河水中含有泥沙的质量,所以它的定义式可写作A =m V ,m 表示太湖湖水中含有泥沙的质量,V 表示湖水的体积。
(2)黄土的密度:ρ=m V =50 g 270 cm3-250 cm3=50 g 20 cm3=2.5 g/cm3。
(3)设含沙量为A ,那么体积为V 的湖水中,黄土的质量为A V ,黄土的体积为A V ρ土,水的体积为V -A ρ土V ,水的质量为ρ水V(1-A ρ土),水与黄土的总质量为ρ水V(1-A ρ土)+A V ,湖水的密度ρ=ρ水(1-A ρ土)+A =ρ水+A -ρ水ρ土A =ρ水+(1-ρ水ρ土)A ,A =ρ土〔ρ-ρ水〕ρ土-ρ水。
14.(1)由题意可知,100 mL 的60度白酒中酒精的体积为60 mL =60 cm3,那么水的体积为100 mL -60 mL =40 mL =40 cm3,水和酒精的质量分别为:m 酒精=ρ酒精V 酒精=0.8 g/cm3×60 cm 3=48 g ,m 水=ρ水V 水=1.0 g/cm3×40 cm3=40 g ,60度〝永新家烧〞的密度: ρ=m V =m 酒精+m 水V 酒精+V 水=48 g +40 g 60 cm3+40 cm3=0.88 g/cm3。
(2)1000 mL 的42度白酒中酒精的体积:V 酒精′=42 mL 100 mL ×1000 mL =420 mL ;设需要60度家烧的体积为V ′,因白酒勾兑前后酒精的体积不变,所以,V ′×60 mL 100 mL =420 mL ,解得:V ′=700 mL 。