题干

Science and Music________ fun.

A:is

B:am

C:are

上一题 下一题 0.0难度 选择题 更新时间:2018-04-08 10:19:26

答案(点此获取答案解析)

C

同类题1

阅读理解

    In high school, all Canadian students take part in a very exciting event. It is "Take Your Children to Work Day". Students will have a chance to work with their parents. My day took place in my mom's work, the York Region Police Department.

    When I arrived, a coach was teaching the officers basic combat(格斗)skills. Everyone tried their best to practice. I could see them sweating and panting (喘气).

    The most exciting part of my visit was a stop at the 911 Communication Center. 911 is the same as 110,119 and 120 in China. Every 911 call in the city is answered here. When I entered the center, I stood beside a call dispatcher (分派人员)arid watched him dealing-with the calls.

    Suddenly, the phone rang, he picked it up and a woman cried for help. There was a robbery in her house. The call dispatcher told her, "Please calm down and move to the safe place quietly. Don't fight with them. Just let them take what they want. Please make sure you are not hurt. We are sending officers there."

    He followed the call and found the address. The call dispatcher chose the five closest police cars from the satellite map and clicked(敲键盘) to send the policemen.  I saw the police cars from the satellite map were quickly moving to the woman's house. Five minutes later, they arrived .I asked the call dispatcher why he sent five cars. He said, "There are different levels of emergencies. Robbery is a high priority (优先),so we have to send five cars." The day was interesting. I leaned how the different departments worked together. The officers were very friendly and admirable.

同类题2

阅读下面的短文,回答问题.

太阳能汽车利用太阳能来驱动,真正实现了零排放.有效地减小了对环境的污染.某太阳能汽车,其前风窗玻璃和顶盖玻璃皆采用防太阳辐射的层压玻璃制作而成,车身轻便灵活.电池完全由太阳能供能﹣通过安装在车顶和前端的电池板收集太阳能.车上太阳能电池板的有效面积为10m2,它正对太阳时电池能够产生100V的电压,并对车上电动机提供20A的电流,电动机最大可获得1600W的机械功率.太阳光照射到地面上1平方米面积上的辐射功率1.0×103W.该车加速性能优越,从静止开始加速100m的路程最短仅需5s.

(1)车窗玻璃能有效防止来自太阳的辐射,主要是能阻挡太阳光中的____ ;太阳能属于____ (选填“可再生”或“不可再生”)能源.

(2)该太阳能汽车在设计时充分利用了流体力学的知识.如图甲所示,当汽车行驶时,流过它上方的空气速度比下方空气速度大,此时,上方空气压强比下方空气压强____ (选填“大”或“小”);该太阳能汽车从静止加速100m路程的过程中可以达到的最大平均速度为____ m/s.

(3)该太阳能汽车电池的输出功率为____ W,将太阳能转化为电能的效率为____ 

(4)若该汽车在水平路面上以最大机械功率P运动,一段时间后再将功率减小到P1,并保持此功率运动,其运动的速度时间图线如图乙所示,设运动过程中小车所受阻力恒定不变;则该车运动时所受阻力为____ N,功率P1=____ W.

(5)该太阳能汽车采用四轮鼓式制动,有效地减小了制动距离.通过测量获得汽车以不同速度行驶时对应的制动距离(即从操纵制动刹车到车停下来的距离),数据如下表所示:

实验次数

1

2

3

4

5

速度/(m•s﹣1

2

3

4

5

6

制动距离/m

0.53

1.20

2.13

3.33

4.80

请在图丙中描点作出s﹣v2图象.根据图象反映的规律可知,当轿车速度为4.5m/s时对应的制动距离是____ m.