近年来，多旋翼无人机发展迅速.由于其机动性和灵活性强，广泛应用在航拍领域、交通管理等方面.如图所示为某品牌四旋翼无人机，它采用4个电机带动旋翼(螺旋桨)转动，对下方空气施力的同时获得升力.该无人机设有一键起降和返航、空中悬停等功能，携带的摄像机可以进行高清拍摄并实时把信号传到遥控器显示器，它还拥有GPS卫星定位系统.下表是该无人机的部分参数：

(1)根据上述内容，下列说法中不正确的是____

A.遥控无人机、卫星定位都是通过电磁波来传递信息的

B.无人机利用了空气对旋翼的反作用力从而获得升力

C.无人机在拍摄地面图像时减小悬停高度可以使图像变大

D.无人机在悬停时不消耗电能

(2)电动机在工作时要保持其两端电压为12V不变，通过电子调速器(简称电调)来控制电动机的电流从而改变电动机的功率，每一个电动机连接一个电调，那么电动机和电调的连接方式是____(选填“并联”或“串联”);若电源电压全部加在电动机和电调的两端，则电动机和电调的功率之比为____.

(3)在电池满容量的情况下，该无人机参与某次火情的勘测时，需要从地面起飞，飞到火场上空60米高处，然后悬停观测(整个过程四个电动机同时工作).由于无人机机动性和灵活性强，这一过程可视为以最大速度匀速直线上升，且达到60米高处时立即静止(悬停).若无人机悬停观测10分钟，电动机将电能转化为机械能的效率为90%，无人机上升过程中所受的阻力为10N，通过计算回答下列问题：(g取10N/kg)

a.从起飞到悬停结束，电动机消耗多少电能?电调部分消耗多少电能?

b.若无人机从60米高处返回到地面，要求电池容量至少剩余10%，若不计其他能量损失，该无人机完成悬停观测后，能否安全返回?

2016年12月20日，中国自主建造的第一艘极地科学考察破冰船(H520)正式开工建造.设计空载排水量为8000t，满载排水量为14000t，它能在覆盖有0.2m厚积雪的1.5m厚冰层上以3.6km/h~7.2km/h的速度连续破冰.(g取10N/kg)

(1)破冰船“H520”用厚钢板做船底，主要是因为钢板具有____(选填序号).①良好的导电性;②较高的硬度;③较高的熔点;④良好的导热性.

(2)假设在1.5m厚的冰层海域以7.2km/h的速度匀速破冰时所受的阻力为2×107N，则根据设计要求破冰船“H520”推进功率多大?

(3)破冰船“H520”可采用“重力破冰法”破冰，“重力破冰法”是指在接触冰面前，船全速航行，船体大部分冲上冰面，就可以把冰压碎，若此时船的排水体积变为原来的七分之二，假设当时破冰船“H520”满载，船与冰层接触面积为5m2，则该破冰船对冰层的压强是多少?(海水的密度取1.0×103

kg/m3)

电阻式传感器被广泛应用与测力、测压、称重，它的核心部分是一只可变电阻，一同学用如图甲所示电路研究某电阻式传感器的特性，图中R0 为定值电阻， R为电阻式传感器，当控制其阻值从0变为60Ω，测得传感器消耗的电功率与通过它的电流关系图象如图乙所示，已知电源电压恒定不变.

(1)当通过传感器的电流为0.1A 时，传感器的电阻为60Ω;

(2)求P1的值;

(3)求R0的阻值.

在水平地面上有一装有特殊液体的圆柱形桶，圆桶与地面的接触面积为0.8m2，筒内液体的密度为0.8 ×103kg/m3，液面飘有一个质量4×10﹣3kg的塑料浮子，桶内液面上方空气和大气相通，整个桶(含液体、浮子)的总质量为96kg.

(1)求圆桶对地面产生的压强;

(2)求塑料浮子排开液体的体积;

(3)若工人师傅利用如图所示滑轮组将圆桶沿竖直方向匀速提升0.5m，滑轮组的机械效率为80%，求该过程中工人师傅所做的总功.

为测定某黄铜(铜、锌合金)中铜的质量分数，称取32.5g该黄铜粉末放入烧杯中，再向烧杯内加入200g 稀硫酸(足量) ，每隔10分钟测烧杯内(不含烧杯)剩余物质的质量，测得数据如表：

(1)完全反应后生成氢气的质量为_____

(2)计算该黄铜中铜的质量分数(写出计算过程)

书面表达。

以一种文具为题按要求写一篇英语小作文。

要求：1.要写出此文具的主要特点。

2.条理清楚，意思连贯，标点正确，书写规范 。

3.不少于50个单词 。

阅读理解，根据短文内容判断正(T)误(F)。

It's Sunday morning. The students of Class 3 are giving their classroom a good cleaning.

Miss Huang, their teacher, is working with them. The children are busy. Some are carrying water;

some are cleaning the windows; others are sweeping the floor. Zhang Hua is putting up a map on the

wall. It is a map of China. Wang Fei and Wei Qing are mending some broken chairs. The children are.

listening to the radio while they are working. The classroom looks nice and bright after the cleaning.

The children are very happy. They go home for lunch at noon.

( ) 1. The children are playing in their classroom on Sunday morning.

( ) 2. Miss Huang, their mother, is working with them.

( ) 3. There is a map of China on the wall.

( ) 4. Two of them are repairing the broken chairs.

( ) 5. They are singing while they are working.

在Ⅱ栏中选出与 Ⅰ栏中相应的答语。

Ⅰ Ⅱ

( ) 1. What's your telephone number, please? A. He is a worker.

( ) 2. It's very cold today, isn't it? B. It doesn't matter.

( ) 3. Can you mend it? C. Yes, wonderful, thanks.

( ) 4. How is your mother? D. Sometimes.

( ) 5. Hi, this is my friend, Lily. E. My telephone number is 6262383.

( ) 6. I'm sorry to trouble you. F. Yes, it is. You need to wear warm clothes.

( ) 7. How often do you go to the park? G. Certainly.

( ) 8. Excuse me. Where is the post office? H. Nice to meet you.

( ) 9. What does your father do? I. She is OK.

( ) 10. Did you have a good trip? J. It's about twenty meters from here.

Jack is a teacher of English. He is not young，but he is not old. He has a round face and black hair.He is tall. There are fifty students in his class. They all like him.Now it's in the afternoon. Look，some students are working in the classroom. Jack is there，too.He is helping them to study English. He is a good teacher， and he is a good friend of them all.

()1. What does Jack do?

A. He is a worker.

B. He is a teacher.

C. He is a doctor.

D. He's a nurse.

()2. What colour is his hair?

A. It's black.

B. His heir is white.

C. It is brown.

D. He has yellow hair.

()3. How many students are there in his class?

A. There are fifteen students in his class.

B. There's fifty.

C. He has fifty.

D. There're fifty in it.

()4. Jack is a good teacher，isn't he?

A. Yes ，he isn't.

B. No ，he is.

C. Yes，he's.

D. Yes ，he is.

()5. What are the students doing in the classroom?

A. They are walking there.

B. They are doing their lessons.

C. They are helping their teacher.

“Early to bed ，early to rise ”makes a man healthy, wealthy and wise.It's good for the body.This is an old saying . Have you heard of it before? It means that we must go to bed early at night，and get up early in the morning.Then we shall be healthy.We shall also be rich and clever.That is true .The body must have enough sleep to be healthy.Children of young age should haveenough sleep ，or they can't do their work very well. They will not be wise and they may not become。wealthy! .The body also needs exercise: walking, running, jumping, swimming, playing games and all other。exercise .Exercise keeps the body strong. Exercise also helps the blood to move around inside the.body .This is very important.Our blood takes food to all parts of our body.The head also needs.blood .Exercise helps us to think better.

根据短文内容 ，回答问题.

1.What does “early to bed .early to rise ”mean?

2.What must the body have to be healthy?

3.What will happen to Children of young age who don't have enough sleep?

4.What keeps the body strong?

5.What takes food to all parts of our body?