问题 问答题

(1)在做“研究平抛运动”的实验时,让小球多次沿同一轨道运动,通过描点法画小球做平抛运动的轨迹.

①为了能较准确地描绘运动轨迹,操作时应注意:调节斜槽使其______,小球应______释放,取点画轨迹时应选取离抛出点比较______的点.

②关于本实验,下列说法正确的是:

A.记录小球位置用的横梁每次必须严格地等距离下降

B.小球运动时不应与木板上的白纸(或方格纸)相接触

C.将球的位置记录在纸上后,取下纸,用直尺将点连成折线

D.实验中,记录小球位置的白纸不能移动

(2)如图为研究小球的平抛运动时拍摄的闪光照片的一部分,其背景是边长为5cm的小方格,重力加速度g取10m/s2.由图可知:照相机的闪光频率为______Hz;小球抛出时的初速度大小为______m/s.B点竖直方向的分速度为______m/s (此题保留两位有效数字)

答案

(1)①只有斜槽的末端保持水平,小球才具有水平初速度,其运动才是平抛运动;每次由静止释放小球,是为了使小球有相同的初速度,所以操作时应注意:调节斜槽使其末端水平,小球应用同一个位置由静止释放,取点画轨迹时应选取离抛出点比较远的点.

②A、因平抛运动的竖直分运动是自由落体运动,在相同时间里,位移越来越大,因此横梁下降的距离不应是等距的.故A错误.

    B、实验要求小球滚下时不能碰到木板平面,避免因摩擦而使运动轨迹改变,故B正确;

    C、将球的位置记录在纸上后,取下纸,将点连成平滑的曲线,故C错误;

    D、因为要画同一运动的轨迹,所以记录小球位置的白纸不能移动,故D正确;

故选BD

(2)在竖直方向上有:△y=gT2,则T=

△y
g
=
(7-5)×0.05
10
s=0.1s.所以f=
1
T
=10Hz;

水平方向做匀速运动,则v0=

x
t
=
5×0.05
0.1
=2.5m/s

B点的竖直方向的分速度vy=

(5+7)×0.05
0.2
=3m/s

故答案为:(1)①末端水平; 从同一个位置由静止释放; 远; ②BD;

(2)10; 2.5m/s;  3.0 m/s

单项选择题
完形填空

阅读下面短文,并按照题目要求用英语回答问题(请注意问题后的词数要求。)

Much meaning can be conveyed, clearly with our eyes, sop it is often said that eyes can speak.

Do you have such a kind of experience? In a bus you may loom at a stranger, but not too long. And if he is sensing that he is being stared at, he may feel uncomfortable.

The same in daily life. If you are looked at for more than necessary, you may look at yourself up and down, to see if there is         ..If nothing goes wrong, you will fell angry towards others' stare at you that way. Eyes do speak, right?

Looking too long at someone may seem to be rude and aggressive. But things are different when it comes to staring at the opposite sex. If a man glances at a woman for more than 10seconds and refuses to avert his gaze, his intentions are obvious, that is ,he wishes to attract her attention, to make her understand that he is admiring her.

However, the normal eye contact for two people engaged in conversation is that the speaker will only look at  the listener from time to time, in order to make sure that the listener does pay attention to what the former is saying, to tell him that he is attentive.

If a speaker looks at you continuously when speaking, as if he tries to dominate you, you will feel disconcerted. A poor liar usually exposes himself by looking too long at the honest communication, quite the contrary.

In fact, continuous eye contact is confined to lovers only, who will enjoy looking at each other tenderly for a long time, to show affection that words can't express.

Evidently, eye contact should be done according to the relationship between two people and the specific situation.

小题1:What is the best title of the passage?(no more than 6 words)

                                                                                

小题2:Please fill in the blank in Paragraph3 with proper words or phrase to complete the sentence.(no more than 10 words)

                                                                                

小题3:Which sentence in the passage can be replaced by the following one?

It may be bad manners to stare at someone.

                                                                                 

小题4:What will you do if your classmates listen to your speaking, according to the passage?(no more than 15 words)

                                                                                

小题5:Translate the underlined sentence into Chinese.