您所在的当前位置：高中物理试题 >

动能定理及应用

> 如图所示，小球的质量为m，悬挂小球的丝线与竖直方向成θ角时，小球恰好在场强为E的匀强电场中静止不动，丝线长度为L．（1）小球带何种电荷，电量是多少？（2）将小球从图示位置拉回到悬线竖直的方向电势能如何变化？（3）若将小球从竖直方向成θ角的位置缓慢拉回到悬线竖直的方向，则拉力做功多少？

问题：

发布时间：2024-09-11

如图所示，小球的质量为m，悬挂小球的丝线与竖直方向成θ角时，小球恰好在场强为E的匀强电场中静止不动，丝线长度为L．
（1）小球带何种电荷，电量是多少？
（2）将小球从图示位置拉回到悬线竖直的方向电势能如何变化？
（3）若将小球从竖直方向成θ角的位置缓慢拉回到悬线竖直的方向，则拉力做功多少？

参考答案：

提问用户：vi***c0z

可能感兴趣的题目：

1 Does this sound familiar? It’s 3:00 am and you’re still awake and staring at the clock. You can’t sleep , and you’ve already tried all the familiar tricks – taken a warm bath , drunk a glass of heated milk ,tried counting sheep, and read a book –all with no success. If you are such a sufferer, remember you’re not alone. Experts said that one in every four Americans have trouble falling or staying asleep. Lack of sleep can hurt your quality of life in so many ways. Short temper, impatience, poor decision-making, and mood swings are common among those with sleeping problems. Besides, relationships with family, friends, and co-workers may suffer as a result. Improper sleep can also put your safety at risk by reducing your awareness. When you’re awake in the middle of the night, you can start to feel desperate for a way out . However, it makes sense to weigh the available treatments before choosing the one that’s right for you. Other sleep aids may seem like a quick fix, but it turns out that there are many disadvantages of these drugs. For one thing, they may require expensive, time-consuming trips to your physician. They may also be habit-forming or have unpleasant side effects like dizziness( 眩晕) dry mouth, and next-day sleepiness. Plus , they become less effective over time. So what is the best sleep aid available on the market today? The answer is Somnapure , a product that represents nature and science coming together. This all-natural sleep aid which comes from Peak Life allows you to fall asleep quickly and remain asleep through the night . With Somnapure, you wake up feeling refreshed and energetic. Somnapure is currently giving away a 14-day trial here. Get your Somnapure trial for better, deeper sleep that you deserve. 小题1:From paragraph 1, we can know that sleep problems are_______. A．easy to make a sufferer lonely B．common but hard to deal with C．severe throughout the world D．widespread only in the USA 小题2:The underlined words“ a quick fix”(in paragraph3)most probably means____. A．a waste of money B．a quick repair C．an easy way out D．a cheap aid 小题3:The purpose of the passage is to _______. A．ask people with sleep problems to try and use Somnapure B．introduce a kind of medicine to help sleep better C．draw people’s attention to the bad effects of the lack of sleep D．talk about what the main causes of the sleep problems are 小题4:We can infer that the passage is probably immediately followed by information about ______. A．the instructions to take Somnapure B．the side effects of Somnapure C．the price of Somnapure D．the way to get Somnapure
2 设函数，，其中实数．（1）若，求函数的单调区间；（2）当函数与的图象只有一个公共点且存在最小值时，记的最小值为，求的值域；（3）若与在区间内均为增函数，求实数的取值范围．
3 下列有关ATP的叙述不正确的是 [ ] A．ATP可作为细胞生命活动的直接能源 B．ATP转化成ADP的过程中需要酶的参与 C．ATP的组成中与脂肪酶相同的元素只有C、H、O D．正常细胞中ATP与ADP之间的转化处于动态平衡
4 21世纪是知识经济时代，为了迎接新的挑战，为了更快地促进科技进步和经济增长，新的时代要求青年学生必须具备知识创新的能力，必须提高国民的素质，培养出德智体美劳等全面发展的社会主义事业的建设者和接班人。为此，我国政府及时提出并制定实施由“应试教育”向“素质教育”转变的教育指导政策。实施“素质教育”是一种正确的价值观，主要是由于它 A．得到社会大多数人的承认 B．符合教育规律和人民的利益 C．是由社会存在决定的 D．减轻了学生的学习负担
5 11月13日，“第四届国家信息化发展论坛”在天津举行，产业部副部长苟仲文在论坛上介绍说：目前我国电话用户总数已接近9亿户，固定电话网和移动电话网规模继续保持世界第一位。市场对固定电话和移动的巨大需求带动了电信行业的蓬勃发展。这说明： A．消费方式决定生产方式 B．消费水平决定生产水平 C．消费对生产具有反作用 D．消费结构决定生产结构
6 薄板的重心位置可以用悬挂法求出．如图所示，先在A点把物体悬挂起来，作出直线AB，然后在D点把物体悬挂起来，作出直线DE，即可知重心在两直线AB、DE交点C处，其实验原理是______．
7 — How do you find the film you saw last night? — ________. I can"t think too highly of it. [ ] A. It"s really splendid. B. It all depends. C. It"s just so so. D. It makes no sense.
8 Let children learn to judge their own work. A child learning to talk does not learn by being corrected all the time; if corrected too much, he will stop talking. He notices a thousand times a day the difference between the language he uses and the language those around him use. Bit by bit, he makes the necessary changes to make his language like other people’s. In the same way, children learn to do all the other things without being taught to walk, run, climb, whistle, ride a bicycle…They compare their own performances with those of more skilled people, and slowly make the needed changes. But in school we never give a child a chance to find out his mistakes and correct them for himself. We do it all for him. We act as if we thought that he would never notice a mistake. If it is a matter in mathematics or science, give him the answer book. Let him correct his own papers. Why should we teachers waste time in such routine(日常的) work? Our job should be to help the child when he tells us that he can’t find the way to get the right answer. Let the children learn what all educated persons must some day learn, how to measure their own understanding, how to know what he does not know. 小题1:According to the passage, the best way for children to learn things is by_____. A．listening to skilled people’s advice. B．asking older people many questions C．making mistakes and having them corrected D．doing what other people do 小题2:Which of the following does the writer think teachers should NOT do?. A．Give children correct answers B．Allow children to mark mistakes. C．Point out children’s mistakes to them. D．Let children mark their own work 小题3:According to the writer, teachers in school should _____ A．allow children to learn from each other B．point out children’s mistakes whenever found C．correct children’s mistakes as soon as possible D．give children more book knowledge 小题4:The passage suggests that learning to speak and learning to ride a bicycle are____ A．different from learning other skills B．the same as learning skills C．more important than other skills D．not really important skills 小题5:The title of this passage could probably be_____ A．Let Us Teachers Stop Work B．Let Us Make Children Learn C．Let Children Correct Their Exercises D．Let Children Learn by Themselves
9 有一测量微小时间差的装置，是由两个摆长略有微小差别的单摆同轴水平悬挂构成．两个单摆摆动平面前后相互平行. （1）现测得两单摆完成50次全振动的时间分别为50.0 s和49.0 s，则两单摆的周期差ΔT＝____________ s；（2）某同学利用此装置测量小于单摆周期的微小时间差，具体操作如下：把两摆球向右拉至相同的摆角处，先释放长摆摆球，接着再释放短摆摆球，测得短摆经过若干次全振动后，两摆恰好第一次同时同方向通过某位置，由此可得出释放两摆的微小时间差．若测得释放两摆的时间差Δt＝0.165 s，则在短摆释放____________ s（填时间）后，两摆恰好第一次同时向____________（填方向）通过____________ （填位置）；（3）为了能更准确地测量微小的时间差，你认为此装置还可以做的改进是______________.
10 近年来，“微博”遍地开花，中国正在进入信息高速传播的新媒体时代。据此回答8～9题。小题1:安徽省某市人大代表全体开设实名微博，把在2011年市“两会”上的建议案发上微博，网友第一时间就可以看到这些人大代表的建议内容，并针对这些建议提出自己的感受和想法。人大代表开微博 A．使网友获得了和人大代表同等的权利 B．是人大代表倾听民意的新渠道 C．是人民当家作主的根本保证 D．是提高人大代表素质的充分条件小题2:在微博中，一些公众人物“语不惊人死不休”，甚至与网友对骂。在信息高速传播的新媒体时代，公民行使权利 A．应做到权利和义务相统一 B．应尽量少发表公开言论 C．享有绝对的言论自由 D．国家不应干涉，否则就侵犯了公民的自由权利