专题滚动检测(十二)

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科学版九年级化学上册滚动专题(一) 空气中氧气体积分数测定的相关探究ppt课件

科学版九年级化学上册滚动专题(一) 空气中氧气体积分数测定的相关探究ppt课件

实验前必须检查装置的气密性,A 正确;铁生锈消耗氧气,使装
置内的气压减小,流入水的体积就是消耗氧气的体积,玻璃瓶内
空气的体积是(250-20)mL=230 mL,进入水的体积是 45 mL,
即氧气的体积是
45
mL











45 mL 230 mL
×100%≈19.6%,B 错误;
滚动专题
(3)装置C、D的实验都用到了红磷,写出反应的文字表达 式:_红__磷__+__氧__气__―_点_―_燃_→__五__氧__化__二__磷___________;反应 结束后,待装置冷却至室温,打开止水夹,装置D中 (试管容积为40 mL),注射器活塞从10 mL刻度处缓 慢移动至___2___mL刻度处停止(误差忽略不计)。
滚动专题
2.【中考·淄博】以下四个实验装置,可用于“测定空气 中氧气的含量”。请认真分析,回答下列问题。
滚动专题
(1)拉瓦锡用装置____A____(填字母)定量研究了空气的成分, 在密闭容器中,空气中的氧气与汞反应,生成固态物 质。人们沿着科学家的足迹,对反应物进行了优化, 分别用铜粉、红磷等进行实验,其原理都是采用 ___化__学___(填“物理”或“化学”)方法,从混合气体中除 去某种气体,从而达到物质的分离。
滚动专题
【点拨】(1)拉瓦锡用装置A定量研究了空气的成分,在密 闭容器中,空气中的氧气与汞反应生成氧化汞;分别用铜 粉、红磷等进行实验,其原理都是类似的,均采用化学方 法。(2)实验过程中,装置B需要不断推拉注射器活塞,以 便反应物与氧气充分接触,使氧气充分反应。造成实验误 差的因素有很多,如药品没有过量、没有冷却到室温就读 数等。

新沪科版八年级物理(下)尖子生课课练——第七章 力和运动 滚动小专题:利用惯性判断物体的运动状态

新沪科版八年级物理(下)尖子生课课练——第七章 力和运动  滚动小专题:利用惯性判断物体的运动状态

滚动小专题——利用惯性判断物体的运动状态一.选择题(共16小题)1.如图为小车载着木块向右运动过程中发生的现象,下列判断正确的是()A.都是小车突然加速时发生B.都是小车突然减速时发生C.图甲是小车突然减速,图乙是小车突然加速D.图甲是小车突然加速,图乙是小车突然减速2.如图所示,我们乘坐的汽车除了前、后排座位都有安全带外,还安装有安全气囊系统,这是为了减轻下列哪种情况出现时对人身造成的伤害?()A.汽车突然启动B.汽车前端发生严重撞击C.汽车速度太慢D.汽车转弯3.在匀速直线行驶的火车车厢里,坐着一位乘客,他发现自己正上方顶棚上有一小水滴正要下落,这滴水将落在()A.此乘客的前面B.此乘客的头上C.此乘客的后面D.此乘客的左侧4.如图所示,是中国科技馆展品“惯性车”。

小火车在平直轨道上匀速行驶,当它将要从“∩”形框架的下方通过时,突然从火车顶部的小孔中向上弹出一个小球,该小球越过框架后,又落回原来的小孔,不计空气阻力。

下列说法中正确的是()第1页(共16页)B.小球能落回小孔是因为它具有惯性,在水平方向与火车保持相同的速度C.若在小球弹出的同时,小火车突然加速运动,小球由于具有惯性,仍能落回原来的小孔中D.若在小球弹出的同时,小火车突然减速运动,小球由于具有惯性,仍能落回原来的小孔中5.如图所示,火车在水平铁轨上匀速直线行驶,车厢内水平光滑桌面上放着物体A、B,A 的质量较大,在火车突然停止时,两物体会由于惯性而运动,在它们离开桌面前()A.一定相碰B.一定不相碰C.可能相碰D.无法判断6.小宇在家观看汽车拉力赛的电视节目,发现汽车行驶速度很快。

其中途经一段“S”形弯道时,如图。

他想:现场观看的观众为了更安全,应站的位置是图中()A.甲、丙B.甲、丁C.乙、丙D.乙、丁7.一架水平匀速直线飞行的飞机以相同的时间间隔分别落下A、B、C三个大小一样的小球,那么反映A、B、C三小球在空中的位置关系正确的图是(不考虑空气阻力)()A.B.C.D.8.气球吊着一个物体匀速上升,突然吊物体的绳断了,绳断后物体的运动状态是()A.由于受到重力,立即下落B.由于小球有惯性,仍然匀速上升C.由于受空气阻力,要悬浮在空中D.先上升再下落9.如图所示,一木块立在表面粗糙的小车上,并随小车一起沿桌面向左做匀速直线运动,当小车遇到障碍物而突然静止时,车上的木块将()A.立即停止运动B.立即向左倾倒C.立即向右倾倒D.继续向左做匀速直线运动10.有两个鸡蛋,一生一熟,让它们在水平桌面上以同样的速度同时开始转动()A.生鸡蛋很快停止转动,熟鸡蛋转了一会儿才停止B.熟鸡蛋很快停止转动,生鸡蛋转了一会儿才停止C.两个鸡蛋都很快停止转动D.两个鸡蛋都转了一会儿,然后同时停止11.摩托车飞越高大障碍物时,为了避免翻车,首先着地的轮子应是()A.前轮B.后轮C.前后轮要同时着地D.哪种着地方式都一样12.如图为我国传统游戏项目打陀螺,在陀螺的锥尖镶嵌小钢珠是为了()摩擦,玩的时候,将鞭子绳绕在陀螺上,迅速抽掉鞭子,陀螺就会飞快地旋转起来,这说明力可以()旋转着的陀螺能保持转动,是因为陀螺具有()A.增大改变物体的运动状态惯性B.增大改变物体的形状运动性C.减小改变物体的形状运动性D.减小改变物体的运动状态惯性13.练习移动射击时,竖直安装并固定一圆形靶,靶的水平和竖起直径将靶面分成四个区域,如图所示,当水平向右平行于靶面运动的汽车经过靶时,车上的运动员枪口对准靶心并立即射击,子弹可能落在()A.Ⅰ区B.Ⅱ区C.Ⅲ区D.Ⅳ区14.大游轮向东匀速直线行驶,小金面朝游轮前进方向,在游轮上的A位置竖直向上起跳,落下时的位置在(不计空气阻力)()A.A位置的东侧B.A位置的西侧C.A位置D.以上三种情况都有可能15.在水平轨道上有一辆实验车,其顶部装有电磁铁,电磁铁下方吸有一颗钢珠。

【K12教育学习资料】全效学习2016版中考数学 第十三单元 投影与视图单元滚动专题九(含解析)

【K12教育学习资料】全效学习2016版中考数学 第十三单元 投影与视图单元滚动专题九(含解析)

第十三单元 投影与视图【测试范围:第十二单元及第十三单元 时间:120分钟 分值:150分】 一、选择题(每题4分,共40分)1.[2015·铜仁改编]请你观察下面四个图形,其中既是轴对称图形又是中心对称图形的是 (C)2.如图1,在Rt △ABC 中,∠BAC =90°,AB =3,AC =4,将△ABC 沿直线BC 向右平移2.5个单位得到△DEF ,连结AD ,AE ,则下列结论中不成立的是 (D )A .AD ∥BE ,AD =BEB .∠ABE =∠DEFC .ED ⊥AC D .△ADE 为等边三角形3.如图2,在△ABC 中,∠B =90°,∠A =30°,AC =4 cm ,将△ABC 绕顶点C 顺时针方向旋转至△A ′B ′C 的位置,且A ,C ,B ′三点在同一条直线上,则点A 经过的路线的长为 (D ) A .4 3 cm B .8 cm C.163π cm D.83π cm【解析】 ∵∠B =90°,∠A =30°,A ,C ,B ′三点在同一条直线上, ∴∠ACA ′=120°.又∵AC =4,∴lAA ′︵=120×π×4180=83π(cm).4.[2015·安徽]下列几何体中,俯视图是矩形的是(B)【解析】 A 的俯视图是圆加圆心;B 的俯视图是一个矩形;C 的俯视图是一个三角形;D的俯视图是个圆.故选B.5.下列图形中,能通过折叠围成一个三棱柱的是 (C)6.小明送给父亲一个礼盒(如图3所示),该礼盒的主视图是(A)图1图2图37.如图4是某几何体的三视图及相关数据,则下面判断正确的是 (D)图4A.a>c B.b>cC.a2+4b2=c2D.a2+b2=c2【解析】此几何体为圆锥,其高为a,母线长为c,底面半径为b,有如下关系:c2=a2+b2,选D.8.[2015·潍坊]如图5所示的几何体的左视图是(C)图59.[2015·营口]如图6,是由若干个相同的小立方体搭成的几何体的俯视图和左视图.则小立方体的个数可能是 (D)图6A.5或6 B.5或7C.4或5或6 D.5或6或7【解析】由俯视图易得最底层有4个小立方体,由左视图易得第二层最多有3个小立方体和最少有1个小立方体,所以小立方体的个数可能是5个或6个或7个.10.如图7所示,如果将矩形纸沿虚线①对折后,沿虚线②剪开,剪出一个直角三角形,展开后得到一个等腰三角形,则展开后的等腰三角形周长是 (D)图7A.12 B.18C.2+10 D.2+210【解析】三角形的底边为2×(10÷2-4)=2,腰的平方为32+12=10,因此等腰三角形的腰为10,因此等腰三角形的周长为2+210. 二、填空题(每题5分,共30分)11.[2015·杭州模拟]如图8,由四个小正方体组成的几何体中,若每个小正方体的棱长都是1,则该几何体俯视图和左视图的面积之和是__5__.【解析】 从左面看第一层有一个小正方形,第二层有一个小正方形,从上面看有三个小正方形,该几何体俯视图和左视图的面积之和是2+3=5.12.[2014·聊城]如图9,点P 是∠AOB 外的一点,点M ,N 分别是∠AOB 两边上的点,点P 关于OA 的对称点Q 恰好落在线段MN 上,点P 关于OB 的对称点R 落在MN 的延长线上.若PM =2.5 cm ,PN =3 cm ,MN =4 cm ,则线段QR 的长为__4.5__cm.【解析】 ∵点P 关于OA 的对称点Q 恰好落在线段MN 上,点P 关于OB 的对称点R 落在MN 的延长线上, ∴PM =MQ ,PN =NR ,∵PM =2.5 cm ,PN =3 cm ,MN =4 cm ,∴RN =3 cm ,MQ =2.5 cm ,NQ =MN -MQ =4-2.5=1.5(cm), 则线段QR 的长为RN +NQ =3+1.5=4.5(cm).13.如图10,将△ABC 沿直线AB 向右平移到达△BDE 的位置,若∠CAB =55°,∠ABC =100°,则∠CBE 的度数为__25°__.【解析】 ∵将△ABC 沿直线AB 向右平移到达△BDE 的位置, ∴△ACB ≌△BED .∵∠CAB =55°,∴∠EBD =55°,则∠CBE 的度数为180°-∠ABC -∠EBD =180°-100°-55°=25°.14.如图11,将△OAB 绕点O 按逆时针方向旋转至△OA ′B ′,使点B 恰好落在边A ′B ′上.已知AB =4 cm ,BB ′=1 cm ,则A ′B 的长是__3__cm.【解析】 根据旋转的性质,得A ′B ′=AB =4cm , ∴A ′B =A ′B ′-BB ′=4-1=3(cm).15.如图12,在等腰Rt △ABC 中,∠A =90°,AC =9,点O 在AC上,且AO =2,点P 是AB 上一动点,连结OP ,将线段OP 绕点O 逆时针旋转90°得到线段OD ,要使点D 恰好落在BC 上,则AP 的长度等于__5__.图12图8图9图10 图11【解析】如答图,过点D作DE⊥AC于E,则∠DOE+∠AOP=90°,∠DOE+∠ODE=90°,∴∠ODE=∠AOP.又∵OD=OP,∠DEO=∠A=90°,∴△DEO≌△OAP,∴DE=OA=CE=2,∴AP=OE=9-4=5.16.[2015·安顺]如图13,正方形ABCD的边长为4,E为BC上的一点,BE=1,F为AB上的一点,AF=2,P为AC上一个动点,则PF+PE的最小值为图13【解析】如答图,作E关于直线AC的对称点E′,连结E′F,则E′F即为所求,过F作FG⊥CD于G,在Rt△E′FG中,GE′=CD-BE-BF=4-1-2=1,GF=4,所以E′F=FG2+E′G2=12+42=17.三、解答题(共80分)17.(10分)画出图14所示物体的三视图(看不见的线用虚线表示).图14解:作图如答图:第17题答图18.(10分)高高的路灯挂在路边的上方,高傲而明亮,小明拿着一根2 m长的竹竿,想量一量路灯的高度,直接量是不可能的,于是,他走到路灯旁的一个地方,竖起竹竿,这时,他量了一下竹竿的影长正好是1 m,他沿着影子的方向走,向远处走出两根竹竿的长度(即4 m),他又竖起竹竿,这时竹竿的影长正好是一根竹竿的长度(即2 m).此时,小明抬头瞧瞧路灯,若有所思地说:“噢,原来第15题答图第16题答图路灯有10 m 高呀!”(如图15所示) 同学们,你觉得小明的判断对吗?解:小明的判断如图,AE ,BF 是竹竿两次的位置,CA 和BD 是两次影子的长. ∵BF =DB =2 m ,即∠D =45°, ∴DP =OP =灯高.在△COP 中,AE ⊥CP ,OP ⊥CP , ∴AE ∥OP ,∴△CEA ∽△COP ,即CA CP =EA OP. 设AP =x ,OP =h 则 11+x =2h①, ∵DP =OP ,∴2+4+x =h ②, 联立①②两式,得x =4,h =10,∴路灯有10 m 高,小明的判断是正确的.19.(10分)如图16是由一些棱长都为1 cm 的小正方体组合成的简单几何体.(1)求该几何体的表面积(包含下底面);(2)该几何体的主视图如图17所示,请在图17方格纸中分别画出它的左视图和俯视图.图17解:(1)该几何体的表面积(含下底面)为26 cm 2; (2)如答图所示:第19题答图20.(10分)某工厂要加工一批茶叶罐,设计者给出了茶叶罐的三视图,如图18,请你按照三视图确定制作每个密封罐所需钢板的面积.(单位:mm)图18 解:由三视图可知茶叶罐的形状为圆柱体,并且茶叶罐的底面直径2r 为100 mm ,高h 为150 mm ,∵每个密封罐所需钢板的面积即为该圆柱体的表面积,图16∴S 表面积=2πr 2+2πrh=2π×502+2π×50×150=20 000π(mm 2).答:制作每个密封罐所需钢板的面积为20 000π mm 2.21.(12分)[2015·杭州模拟]如图19,△ABC 和点S 都在正方形网格的格点上,每个小正方形的边长为1.(1)将△ABC 绕点S 按顺时针方向旋转90°,画出旋转后的图形△A 1B 1C 1; (2)求弧BB 1的长;(3)请求出△ABC 旋转到△A 1B 1C 1扫过的面积.图19解:(1)∵△ABC 绕点S 按顺时针方向旋转90°得到△A 1B 1C 1, ∴AB =A 1B 1,BC =B 1C 1,AC =A 1C 1,SC ⊥SC 1,SB ⊥SB 1,SA ⊥SA 1, 故可画出旋转后的A 1B 1C 1,如答图所示;第21题答图(2)∵BS =32+22=13,∴弧BB 1的长=90·π·13180=13π2;(3)∵AS =52+12=26,CS =22+12=5,∴△ABC 扫过面积=S △ABC +S 扇形ASA 1-S 扇形CSC 1 =12×3×2+90·π(26)2360-90·π·(5)2360=3+214π.22.(14分)[2015·湖州模拟]已知:在△ABC 中,AD 为中线,如图20①,将△ADC 沿直线AD 翻折后点C 落在点E 处,连结BE 和CE . (1)求证:BE ⊥CE ;(2)若AC =DC (如图②),请在图②中画出符合题意的示意图,并判断四边形ADBE 是什么四边形?请证明你的结论.图20解:(1)证明:∵△ADC 沿直线AD 翻折后点C 落在点E 处, ∴△ADC ≌△ADE , ∴CD =ED ,∴∠DCE =∠DEC , ∵AD 为△ABC 的中线, ∴BD =DC , ∴BD =DE ,∴∠DBE =∠DEB ,∵∠DBE +∠BEC +∠ECB =180°, 即2∠DEB +2∠CED =180°, ∴∠DEB +∠CED =90°, ∴BE ⊥EC ;(2)如答图,ADBE 是平行四边形.理由如下: ∵△ADC 沿直线AD 翻折后点C 落在点E 处, ∴△ADC ≌△ADE , ∴AE =AC ,DE =DC ,∵AC =DC ,∴AE =AC =DE =DC , ∴AEDC 是菱形,∴AE ∥DC ,且AE =DC ,∵AD 是△ABC 的中线,∴BD =DC , ∴AE ∥BD ,且AE =BD , ∴ADBE 是平行四边形. 23.(14分)[2015·杭州模拟]如图21,△ABC 是正三角形,且边长为1,点E 是直线AB 上的一个动点,过点E 作BC 的平行线交直线AC 于点F ,将线段EC 绕点E 旋转,使点C 落在直线BC 上的点D 处,当点E 在△ABC 的边AB 上时. (1)求证:AE =BD ;第22题答图图21(2)设梯形EDCF 的面积为S ,当S 达到最大值时,求∠ECB 的正切值. 解:(1)如答图,在正△ABC 中,∠ABC =∠ACB =∠BAC =60°,AB =BC =AC , ∵EF ∥BC ,∴∠AEF =∠AFE =60°=∠BAC , ∴△AEF 是正三角形, ∴AE =AF =EF ,∴AB -AE =AC -AF ,即BE =CF , 又∵∠ABC =∠EDB +∠BED =60°, ∠ACB =∠ECB +∠FCE =60°, ∵ED =EC ,∴∠EDB =∠ECB ,∴∠BED =∠FCE ,∴△EDB ≌△CEF , ∴DB =EF ,∴AE =BD ;(2)如答图,过点E 作EH ⊥DC 于点H , 设AE =x ,则S =12(EF +DC )×EH=12(x +x +1)×32(1-x ) =-32x 2+34x +34, 当x =14时,有最大值;此时,EB =34,则EH =338,BH =38,CH =58,tan ∠ECB =EH CH =33858=335.第23题答图。

专题5 绿色植物的生命活动(基础检测卷)-备战2020年中考生物专题滚动双测卷(解析版)

专题5 绿色植物的生命活动(基础检测卷)-备战2020年中考生物专题滚动双测卷(解析版)

专题5 绿色植物的生命活动基础检测卷班级___________ 姓名___________ 学号____________ 分数____________(考试时间:90分钟试卷满分:100分)一、选择题:本题共25个小题,每小题2分,共50分。

在每小题给出的四个选项中,只有一项是符合题目要求的。

1.在炎热的环境中,树荫下比较凉爽,原因之一是由于树木()A.进行呼吸作用的缘故B.通过蒸腾作用散失水分造成的C.进行光合作用的结果D.大量吸收水分和无机盐的结果【答案】B【解析】植物的蒸腾作用是指植物体内的水以水蒸气的形式散发到大气中去的过程,水由液态到气态要吸收热量,因此在此过程中能带走植物体内的热量,降低植物体的温度,继而降低环境的温度,因此在炎热的夏季,树林里凉爽宜人。

可见B符合题意。

2.“绿叶在光下制造有机物”的实验中,把叶片放入酒精内隔水加热的目的是()A.分解淀粉B.溶解淀粉C.将淀粉煮沸D.把叶绿素溶解到酒精中【答案】D【解析】酒精能溶解叶绿素,而且酒精是易燃、易挥发的物质,直接加热容易引起燃烧发生危险。

使用水对酒精进行加热,起到控温作用,以免酒精燃烧发生危险。

因此“在‘绿叶在光下制造有机物’的实验中”,把叶片放入酒精中隔水加热的目的是“溶解叶绿素,避免酒精燃烧起来”。

3.既是植物蒸腾作用的“门户”,又是气体交换的“窗口”得结构是()A.叶片B.叶肉C.叶绿体D.气孔【答案】D4.移栽树木时,与降低蒸腾作用无关..的措施是( )A.进行遮阳B.阴天移栽C.合理施肥D.减少叶片【答案】C【解析】移栽植物时,选择阴天移栽植物、剪去部分枝叶、并对移栽后的植物进行遮荫等做法,都是为了降低植物的蒸腾作用,减少水分的散失,提高植物的成活率;合理施肥是为了给植物的生长提供营养,与蒸腾作用无关,C不符合题意,故选C。

5.大棚种植的西瓜喜获丰收,合成西瓜中甜味物质的原料是( )A.二氧化碳和水B.二氧化碳和氧气C.水和有机物D.氧气和无机盐【答案】A【解析】光合作用是绿色植物把二氧化碳和水合成有机物,释放氧气,同时把光能转变成化学能储存在合成的有机物中的过程。

培优专题(三) 平面图形的滚动问题

培优专题(三) 平面图形的滚动问题
第二十四章
培优专题(三)

平面图形的滚动问题
方法管理 归类探究
方法管理
平面图形的滚动问题,实际上是物体的旋转,问题通常包括求滚动轨迹, 求围成图形的面积或者周长等方面;又涉及在直线上滚动、在平面图形外部滚 动和在平面图形内部滚动等类别. 求解这类问题的关键点是弄清楚滚动的轨迹, 同学们常常因画不出滚动的轨迹而无从下手,只能凭空猜测.
图1
解:(1)Rt△ABC 中,AB= AC2+BC2=2, ∴∠BAC=30° ,则∠ABC=60° ,∴∠ABA′=120° , 120π×2 4π ∴A 到 A′的路线长为 180 = 3 . 又∵∠A′C′A″=90° , 90π× 3 3 ∴A′到 A″的路线长为 180 = 2 π, 4 3 ∴点 A 所经过的路线长为3π+ 2 π.
归类探究
类型之一 三角形的滚动 如图 1, 把 Rt△ABC 的斜边 AB 放在直线 l 上按顺时针方向在 l 上转 动两次,使它转到△A″B′C′的位置.若 BC=1,AC= 3,当顶点 A 运动到 点 A″的位置时. (1)求点 A 经过的路线有多长; (2)求点 A 经过的路线与直线 l 所围成的面积.
解:当正方形 ABCD 滚动一周时,所经过的路径是由三段圆弧组成. 第一段是以第一个点 C(即第一次滚动时点 C 的位置)为圆心,以 AC 长为 半径的一段弧, 第二段是以第二个 D 点为圆心,以 AD 长为半径的一段弧, 第三段是以第四个点 B 为圆心,以 AB 长为半径的一段弧. 因为每次滚过的角度均为 90° ,所以其弧长均为弧所在的相应的圆的周长 1 的4, 1 所以当正方形滚动两周时,正方形的顶点 A 所经过的路线的长是 2×4 (2× 2×8π+2×8π+2×8π)=(16π+8 2π)cm.

2024年中考物理专题训练——运动和力实验(含答案)

2024年中考物理专题训练——运动和力实验(含答案)

2024年中考物理专题训练——运动和力实验1.在“探究阻力对物体运动的影响”时,利用的器材有斜面、木板、玻璃板、棉布和小车,如图所示.(1)小车每次从斜面上的同一位置开始下滑,使小车进入水平部分时大小相等.(2)下面是记录实验情况的表格,请你将其中(a)、(b)两项内容补充完整.(3)推理:小车在绝对光滑的水平面上运动,即不受阻力作用,小车将做运动.水平部分的材料有木板、玻璃板和棉布,为便于推理,水平部分材料的摆放顺序最好依次为.2.某同学在探究弹簧的特点时,得出了弹簧的长度与弹簧受到的拉力的关系如图所示,请回答下列问题:(1)这根弹簧的原长是cm;(2)弹簧在受到6N的拉力时,弹簧比原来伸长了cm,此时弹簧发生了形变;(3)分析图象中及有关数据,可得出的结论是在一定范围内,弹簧的伸长量与拉力大小成比,根据这个原理制成了.3.在探究“力和运动的关系”的实验中:(1)为探究小球滑行距离与水平面粗糙程度的关系,图A实验中小宇先后三次将小球从同一斜面上的同一高度处由静止释放,这样操作的目的是.(2)在上述三次实验中若不考虑空气阻力影响,则小球在三种不同材料的表面上克服摩擦力做的功(选填“相等”、“不相等”或“无法判断”).(3)为了模拟研究汽车超速带来的安全隐患,小斌同学设计了如图B所示的探究实验.将质量相等的A、B两个小球先后从同一斜面的不同高度由静止滚下(h A>h B),推动同一小木块在相同的水平面上运动不同的路程.两次实验中,木块滑动时受到的摩擦力分别为f甲、f乙,则f甲 f乙(选填“>”、“<”或“﹦”).甲实验中小球对木块做功多,是因为A球在水平面上的能大.4.爱米同学发现爸妈同时买了新鞋,她很好奇,想知道谁的新鞋防滑更好。

于是爱米找来一个弹簧测力计、两个粘钩,进行如下探究:(1)如图爱米将粘钩分别粘在两只新鞋跟上,放在同一块水平地板上,分别用弹簧测力计沿着方向拉动,使之做运动,测出滑动摩擦力大小进行比较。

中考数学专题复习《实数》检测题真题(含答案)

中考专题复习实 数1、有理数:像3、53-、119……这样的 或 。

2、数轴:规定了 、 和 的直线叫做数轴(画数轴时,要注意上述规定的 三要素缺一不可)。

3、相反数:只有 不同的两个数,如a 的相反数是 ,0的相反数仍是 。

若a 与b 互为相反数,则 .4、绝对值:正数的绝对值是它 ,负数的绝对值是它的 ,0的绝对值是0.任何实数的绝对值都是 ,a ≧0.互为相反数的两个数的绝对值相等,a =a -。

5、倒数: 没有倒数。

正数的倒数是正数,负数的倒数是负数。

若a 与b 互为倒数,则 .6、有理数的四则混合运算:(1)先乘方,再乘除,最后加减; (2)同级运算,从左到右进行;(4)如有括号,先做括号内的运算,按 ,中括号, 依次进行。

7、乘方:求n 个 的积的运算,叫做乘方,乘方的结果叫做 。

在a n中,a 叫做 ,n 叫做 。

8、科学记数法:把一个数写做 的形式,其中101<≤a ,n 是整数,这种记数法叫做科学记数法。

9、平方根:如果一个数的平方等a ,那么这个数叫做a 的 或 ,0的平方根是0,负数 平方根。

a 的平方根记为a ±(a ≧0),读作“正负根号a ”,a 叫做被开方数。

10、算术平方根:如果一个正数的平方等于a ,那么这个正数叫做a 的 ,0的算术平方根为0。

a 的算术平方根记为a (a ≧0),读作“根号a ”,a 叫做被开方数。

11、立方根:如果一个数的立方等于a ,那么这个数叫做a 的 或 ,0的立方 根是0,正数的立方根是正数,负数的立方根是负数。

3a -=3a ,a 的立方根记为3a ,读作“三次根号a ”,a 叫做 ,3是 。

知识回顾12、无理数:像2、33、……这样的 。

13、实数: 和 统称为实数。

实数与数轴上的点 。

1.(2017湖南长沙,1)下列实数中,为有理数的是( ) A .B .C .D .12.(2017广东广州,1)如图1,数轴上两点表示的数互为相反数,则点表示的( )A . -6B .6C . 0D .无法确定3.(2017湖南长沙,3)据国家旅游局统计,2017年端午小长假全国各大景点共接待游客约为82600000人次,数据82600000用科学记数法表示为( ) A .B .C .D .4.(2017山东临沂,1)的相反数是( ) A .B .C .2017D .5.(2017浙江宁波,4)实数的立方根是 .6.(2017重庆A 卷,13)“渝新欧”国际铁路联运大通道全长11000千米,成为服务“一带一路”的大动脉之一,将数11000用科学记数法表示为 . 7.(2017重庆A 卷,14)计算:|﹣3|+(﹣1)2= . 8.(2017江苏徐州,9)的算术平方根是 . 9.(2017浙江嘉兴,17(1))计算:.10.(2017浙江台州,17)计算:.基础检测考点精讲1.有理数概念【例题1】(2017河南,1)下列各数中比1大的数是()A.2 B.0 C.-1 D.-3【答案】A,【解析】根据正数大于0,0大于负数,两个负数,绝对值大的反而小可得题目选项中的各数中比1大的数是2,故选A.【考点】有理数的大小比较.【变式】(2017重庆A卷,14)计算:|﹣3|+(﹣1)2= .【答案】4.【解析】|﹣3|+(﹣1)2=4【考点】有理数的混合运算.【例题2】(2017天津,1)计算的结果等于()A.2 B. C.8 D.【答案】A.【解析】根据有理数的加法法则即可得原式-2,故选A.【变式】(2017山东滨州,1)计算-(-1)+|-1|,结果为()A.-2 B.2 C.0 D.-1【答案】B.【解析】原式=1+1=2,故选B.【例题3】(2017山东日照,3)铁路部门消息:2017年“端午节”小长假期间,全国铁路客流量达到4640万人次.4640万用科学记数法表示为()A.4.64×105B.4.64×106C.4.64×107D.4.64×108【答案】C.【解析】科学记数法的表示形式为a×10n的形式,其中1≤|a|<10,n为整数.确定n的值是易错点,由于4640万有8位,所以可以确定n=8﹣1=7.4640万=4.64×107.故选:C.【考点】科学记数法—表示较大的数.【变式】(2017辽宁沈阳,3)“弘扬雷锋精神,共建幸福沈阳”幸福沈阳需要830万沈阳人共同缔造。

轴承培训专题教育课件


有关圆柱滚子轴承旳类型代号
•NU型-外圈有档边,非定位轴承 •N型-内圈有档边,非定位轴承 •NJ型-外圈有档边,内圈一侧有
档边,单向定位
•NUP-比NJ型多一种活动档边,
双向定位
●NU+HJ内圈无挡边但有斜挡圈能够与组 件分离
October 30, 2023 © SKF Group Slide 20
推力轴承 高度系列代号 79 1 2
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轴承旳型号编制
轴承旳内径代号措施
轴承公称内径
内径代号
0.6--10(非整数)
5.挡圈 、防尘罩
October 30, 2023 © SKF Group Slide 9
轴承旳保持架
为了满足保持架旳分隔、引导、保持作用,保持架旳材料要有 一定旳钢性、强度、耐磨性、耐冲击性、润滑性和储油性。保持架 旳强度和精度影响到轴承旳寿命和旋转精度。
冲压架保持架: 结实、耐高温 尼龙保持架: 运营速度高、低噪音 铜保持架: 结实、用于振动环境
用公称内径毫米数字 直接表达,与尺寸系 列代号之间用”/”隔 离
1--9(整数)
用公称内径毫米直接 表达,对深沟轴承及 角接触轴承7\8\9直 径系列用”/”隔离
10
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12
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15
02
17
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20--480(22 28 32除外)
October 30, 2023 © SKF Group Slide 22

人教版九年级下册化学 第九单元 溶液 滚动小专题(二) 溶解度及溶解度曲线


【解析】 t1℃时,相同质量的甲与丙两种物质的饱和溶液中溶质 质量相等,故A错误;乙溶解度受温度变化影响小,降 低温度时甲物质的溶解度变化较大,则乙中混有少量甲 时,应采用蒸发结晶的方法提纯乙,故B项错误;20 ℃ 时,溶解度大于10g的物质为易溶物质,根据图像,0 ℃ 时甲物质的溶解度为10 g,且随温度的升高,甲物质的 溶解度不断增大,所以甲属于易溶物质,故C正确; t2℃时,甲的溶解度为50 g,则在50 g水中最多只能溶解 25 g甲,形成75 g溶液,故D项错误。
减小,会析出晶体,溶质质量分数会减小,但t2℃时丙的溶解度 大于t1℃时甲的溶解度,故两种溶液中的溶质的质量分数丙大于 甲,B错误;甲的溶解度随温度的升高而增大,将t2℃时甲的饱和 溶液变为t3℃时甲的饱和溶液,可以采用蒸发水的方法,C正确; t3℃时三种物质的溶解度关系为甲>乙>丙,将t3℃时三种物质的 饱和溶液恒温蒸发等量水后,析出溶质的质量甲>乙>丙,D正确。
典例1 (2015•河北)甲、乙、丙三种固体物质的溶解度曲线如图所示,下 列叙述错误的是( B )
A.t1℃时,将等质量的甲、乙分别配成 饱和溶液,所得溶液质量:甲>乙
B.将t1℃时甲、丙的饱和溶液升温到t2℃, 两种溶液中溶质的质量分数相等
C.将t2℃时甲的饱和溶液变为t3℃时甲的饱和溶液,可以采用蒸 发水的方法
【解析】 比较②③数据可知,②中所得溶液是不饱和溶液,故A
错误;20 ℃ 时10 g 水最多溶解3.6 g NaCl,故B错误;
由表中数据可知,③④溶液都是饱和溶液,在相同温度
下,同种物质的饱和溶液的溶质质量分数相等,故C正
确;①所得溶液的溶质质量分数为
2g 100% 16.7% 2g+10g

高三英语复习专题滚动检测18

专题滚动检测(十七)(限时:37分钟语法填空2篇+阅读理解2篇+短文改错) Ⅰ.语法填空AMother Teresa was born in Yugoslavia, on August 27, 1910. She attended the government school near her home until she was eighteen. At that time, some doctors and nurses from Yugoslavia were 1.________(work) in India,and they often wrote to the school about their work.She decided to join 2.________ one day.When she left school, she 3.________went to Britain; then a year later she went to India,where she began to 4.________ (train) to be a teacher. After training, she was sent to Calcutta, 5.________ she taught geography at a school and soon after became the headmistress (女校长).However, 6.________she loved teaching, in 1946 Mother Teresa left the school and went to work in the poor parts of Calcutta. Later she was trained to become a nurse in Patna, and then began her work helping the 7.________and comforting the dying in the streets of the city. Slowly, 8.________came to help her, and her work spread to other parts of India.Mother Teresa was a well-known person forever. Many photos were taken of her, as she travelled around 9.________world to open new schools and hospitals in poor countries. In 1979, she 10.________(give) the Nobel Prize for the lifetime of love and service she had given to the poor.BM:There are many things that are better about living in the city! It is also 1.________(interesting).W:Yes, 2.________the city is more dangerous than the country.There are often many bad things 3.________ happen in the city, such as robberies.M:That's true. Sometimes people in the city aren't as open and friendly as 4.________in the countryside.W:Besides that, the city is very noisy.When I was young, I always 5.________(want) to escape the city life to have a good rest and enjoy 6.________beautiful scenery in the country!M:Yes, the city is busier and noisier than the country. 7.________,the country is much slower than the city.Oh, I don't think it is a good thing. The country is so slow and 8.________(bore)!W:What about the cost of living? Is it lower in the country than that in the city?M:Oh, yes. It is higher in the city.W:Life in the country is also much healthier than that in the city.M:Yes, 9.________is cleaner and less dangerous in the country. Well, I'm young now. Maybe when I am 10.________(marry) and have children I'll move to the country.Ⅱ.阅读理解A(2014·深圳高三第二次调研)A Korean wave is sweeping across China, with many Chinese women worshiping South Korean actors Kim Soo Hyun and Lee Min Ho as demigods (被神化的人物). Chinese netizens always have different opinions on South Korean TV dramas, but there is no doubt that programs from the neighboring country are now enjoying a new round of popularity in China. And a big part of the credit for that goes to You Who Came from the Stars, the South Korean TV series which is on the air now.You Who Came from the Stars and The Heirs (《继承者们》) have been subjects of hot online discussions throughout Asia.Besides, the book, The Miraculous Journey of Ed w ard Tulane, read by the hero in You Who Came from the Stars was a hard-to-get item on Amazon for a while.The two TV programs have several common elements (要素): a tall, handsome, and rich hero who loves the heroine blindly and always protects her, and an equally handsome man madly in love with the same woman.Both programs describe the purity of love, which is expressed through a kiss or a warm hug.Perhaps that's the secret of their success; perhaps people still like Cinderella-type stories.The widening wealth gap is a matter of social concern both in South Korea and China, and the challenges that young people face in their hope for a better life might have caused many ordinary girls to dream of marrying rich, caring men.This is precisely what the popular South Korean TV dramas describe. In_fact,_South_Korean_TV_dramas_are_tailored_to_meet_the_market's_demands.Many netizens even said at an earlier time that South Korean TV dramas had become popular because of their stereotyped (模式化的) themes: traffic accidents, cancer and other incurable diseases.But all that has changed with the success of You Who Came from the Stars and The Heirs, which Chinese directors can use as examples, as well as inspiration, to improve their productions.1.What is the main reason for a new round of popularity in China?A.The dramas are from the neighboring country North Korea.B.Most of the Chinese netizens have voted for them.C.The actors in the dramas are all gods.D.It is because of You Who Came from the Stars.2.Which is NOT included in the elements for the success of South Korean dramas?A.Charming pure love stories.B.A tender kiss and a warm hug.C.Handsome and rich heroes.D.The heroine's blind love with the rich.3.The underlined sentence in Paragraph 4 means that they are designed to ________.A.develop in a large scaleB.be measured to a certain sizeC.meet popular taste purposelyD.be shown in a big market4.The main purpose of stereotyped themes in South Korean dramas is to________.A.present an idea B.attract TV viewersC.make them colorful D.arouse some challengesBFor half my life, I dreamed of attending Vanderbilt. In 2011, I chose to attend Vanderbilt University for my Master of Education in Elementary Education. Often referred to as being part of the Southern Ivy League, Vanderbilt is a top school of the south. Peabody College of Education has been ranked a top university for studying education many years in a row. When I applied, I had a mission to help educate students in my rural hometown of Nashville.In my graduate school program, I wanted to be surrounded by hard workers to help me become the best I could be in my field. I was excited to have Vanderbilt offer me scholarships to cover a little over a third of my schooling. I wanted to go to Vanderbilt because of the school's severeness and reputation. My program required a full time schedule. Finishing the program took a year and a half to graduate. With a busy course schedule, I felt very refreshed and focused. I participated in volunteer work as well as the required practices and student teaching. Volunteering with students who had special needs was one of the most meaningful experiences I had. Learning about students with disabilities was so moving to me that I encouraged my daughter to donate D|S500 to the Vanderbilt Kennedy Center.Regarding the severeness of the program at Vanderbilt, professors hold students up to high expectations. I had to get used to not always making As. I always hold myself up to high expectations. I learned to show constant improvement, and I realized that understanding my weaknesses was the key to improvement. When I passed my Teacher Performance Assessment, I realized how much content the program had taught me.Earning my Master of Education degree from Peabody College of Education at Vanderbilt University helped place a sense of confidence in me. I received 10 interviews in some of the mostprestigious (有声望的) private elementary and middle schools in the country the summer after graduation. As I knew professionals who were having a hard time getting one interview in this economy, I was excited to receive so much attention. Currently, I whole-heartedly love the field of education.5.What is the last purpose of the author in going to Vanderbilt?A.Gaining Vanderbilt's scholarship.B.Being a teacher in his hometown.C.Succeeding in attending Vanderbilt.D.Earning the Master of Education degree.6.The severeness of the program at Vanderbilt lies in ________.A.teaching students a great deal of contentB.allowing students not to attain As at timesC.helping students overcome their weaknessD.setting up higher goals for students to reach7.Why did the author feel excited in the last paragraph?A.He received 10 interviews in some schools.B.He found a job in a prestigious high school.C.He had a sense of confidence in himself then.D.He got his Master of Education degree at last.8.We can learn from this passage that ________.A.the author must have graduated from the high school in 2011B.the author's Teacher Performance Assessment was difficult to passC.the author finished his education wholly depending on his scholarshipD.Vanderbilt University is referred to as the best of the Southern Ivy LeagueⅢ.短文改错On my way to the bookstore, I noticed a group of people surrounded two anxious foreigners.I stopped and found that they were tourist from Canada who careless left a very important wallet in a taxi. I accompanied them to the nearest police station and without their help, we got in touch with the taxi company. We told a moment ago a driver had just turned in a wallet and then a policeman drive us to the company without delay. The two Canadians happily claimed their wallet, that contained their passports, flight tickets, some cash or credit cards. They expressed our thanks to me. I feel it is really a great pleasure to help the others.答案Ⅰ. A1.解析:working考查非谓语动词。

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专题滚动检测(十二)(限时:37分钟语法填空2篇+阅读理解2篇+短文改错) Ⅰ.语法填空AToday I received a sweet letter from Brianna, one of my “cookies”. You see 1.________ I taught kindergarten, I called all 2.________ sweet children“cookies”. Brianna said that every day she would walk into kindergarten and see a smile 3.________ my face. It wasn't difficult to have a smile on my face 4.________ almost every day I was going to see my sweet“cookies”. I named them“cookies”because I always feel that children bring great happiness and 5.________ (excite) to my life. 6.________ after adopting two sons from Russia in 1994 and 1996, I still felt that all children were the greatest joy I could 7.________ have. I adopted and taught children for over 35 years. All my children were 8.________ are now a great joy of my life. I feel 9.________ (great) fortunate to be able to use my life's talent to teach children and have fun 10.________ (do) it every day. I am able to spread my wings and help my “cookies” to spread their wings.BMan:Oh, calm down. What's 1.________?Woman:Someone broke into my apartment yesterday and many items of mine 2.________ (steal).Man:Oh, don't worry. We will deal with it, 3.________ first we need to have your basic information, so what's your name?Woman:Emily Young.Man:Could you 4.________ your family name please?Woman:OK, Y-O-U-N-G, Young.Man:Y-O-U-N-G. OK, then what's your address?Woman:No, 306, Fifth Avenue.Man:And your 5.________ (nation)?Woman:Canadian.Man:OK. let's know about the lost items. 6.________ have you lost?Woman:A laptop (笔记本电脑), a cellphone, and a wallet.Man:OK. What are the brands (品牌) and models of your laptop and cellphone? And 7.________ money was in the wallet?Woman:The laptop's model is SH462513, and the cellphone is iPhone 5. Oh ... the cash in my wallet, let me think, is 8.________ (probable) 200 dollars. And there are many important materials in my laptop. Please help me find it.Man:OK, and your phone number?Woman:Um ... 2237676, but I'm only there after about 7:00 pm.Man:So when would be the 9.________ (good) time to catch you?Woman:I suppose between 9:00 pm and 9:30 pm.Man:OK, I see. We'll let you know if 10.________ have any information.Ⅱ.阅读理解A(2014·长春一中模拟)Playing the piano may seem like nothing special to you, but what about playing it on bananas instead of piano keys? Lin Hai, a 24-year-old graduate did exactly that with his homemade electronic board.Wearing thick glasses and a simple T-shirt, Lin looks no different from other engineering students. When Lin was little, he loved taking machines in his home apart to look at how they worked. Even though he often failed in putting them back together, his curiosity was never satisfied and he laid hands on everything. When he went to university, Lin chose a subject that was related to engineering and programming: automation.Lin is a typical geek (极客) who often spends days in the laboratory inventing new things. “I have a lot of ideas in my head. My biggest interest is realizing them,”says Lin. His inventions include a guide robot, an earthquake alarm and an electronic door lock. But his most successful invention is an electronic board he calls “Crazyer”,the one that turns bananas intopiano keys.Lin Hai's Crazyer electronic board was inspired by a similar device (装置) built by two PhD students at MIT. Their device is called Makey Makey, which turns everyday objects into touchpads (触屏装置). Having seen a video, Lin was so impressed by the device that he searched for its website in the hope of buying one. It turned out to be a prototype (样机), and Lin would have needed to wait for six months for the real product.“Why not make my own Makey Makey?”he thought. So he studied the video and website, trying to figure out how it worked. His hard work paid off.With the money he earns from selling Crazyer, Lin can give back to society. “Crazyer can help those who have lost their fingers or limbs,” says Lin. “With Crazyer, some people can use their feet or arms to use a computer.”Another benefit is that the money he earns can support Lin in inventing new things. “I'm thinking of adding new functions to Crazyer. And there is a long way for me to make it,” he says.1.From the passage, we can learn that ________.A.Lin is expert at playing the pianoB.Lin's curiosity made his parents very angryC.Lin and other engineering students are the same in appearanceD.Lin showed his interest in machines when he wasyoung2.Which of the following are Lin's inventions?a.a guide robot b.Makey Makeyc.an earthquake alarm d.an electronic door lockA.a, b, c B.a, b, dC.a, c, d D.b, c, d3.We can infer from the passage that Crazyer ________.A.is designed for computer loversB.is of great use for disabled peopleC.made Lin very popular among his classmatesD.cost Lin a lot of money and time to invent it4.What will the author most probably talk about if the passage continues?A.The disadvantages of Crazyer.B.Why Lin likes to invent new things.C.How Lin adds new functions to Crazyer.D.The history and development of Crazyer.BKenji Croman has broken his bones, his shoulder and elbow, and nearly drowned several times. He's also had three close encounters with sharks over the years. A 10-foot wave landed directly on top of him five years ago, bending his body to the point that he actually kicked himself in the head. “I literally heard every bone in my body crack,” he said.Croman has been photographing ocean waves since 2008, sometimes risking his life to get that perfect shot at the surf break. Despite the risks and certain injuries that come with wave photography, the Hawaii resident, body surfer and former competitive swimmer wouldn't do anything else. The 36-year-old photographer loves the thrill of meeting breaking waves head on, shooting waves as his interest and shooting surfers to pay the bills.“The process of photographing waves requires more than just swimming out where the surf breaks and waiting,” he says. The night before a photo shoot Croman checks , a website and the coastal camera network that provides live and predicted ocean weatherinformation, to see what the winds, waves and tide will be like at certain times. Croman has both a primary camera and a backup for emergencies. He goes without a wetsuit and uses a heavy duty underwater housing to protect his camera. There is no great way for him to protect himself. He admits there are probably protective clothes he should be wearing, but there is little he could have done to decrease the impact of the 10-foot wave that crashed on top of him.The hardest part of Croman's job is staying calm in the face of breaking waves when his initial reaction is to panic and swim away. At most, Croman will take two to three shots of a single wave. “I've shot waves for so many years now that I see the wave in slow movement, ” he said.5.How does Kenji Croman make a living?A.By taking swimming races.B.By teaching photography.C.By shooting surfers.D.By surfing waves.6.Why does Kenji Croman check the websites like ?A.To get better prepared for shooting.B.To predict something about weather.C.To learn more about surfing waves.D.To buy better equipment for safety.7.What is the biggest problem for Croman in his own eyes?A.Staying away from shark attacks.B.Protecting himself from getting hurt.C.Taking good care of his cameras.D.Staying calm facing breaking waves.8.What would be the best title of the text?A.Taking adventures around the oceanB.Risking his life for the perfect waveC.Making preparations for life risksD.Appreciating breaking waves in dangerⅢ.短文改错I prefer my English classes to be taught in English only. What we all know, a good learning environment is of greatly importance if we want to study English well. Classes teaching in English provide students for a better environment. When English is an only language in class, students will have more opportunity to practise listening and speaking. However, there were problems with this method. Sometimes we may find difficult to follow the teacher and some slow learners may even give up learn English. In spite of these difficulties, but I believe practice makes perfect. With enough practice, we can overcome the difficulties and benefit from English classes in the long run.答案1.解析:when考查连词。

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