九年级新课：机械能的概念及动能和势能转化

九年级新课：机械能的概念及动能和势能转化 九年级新课:机械能的概念及动能和势能转化 二. 重点、难点: 理解动能和势能的相互转化。 (1)知道动能和重力势能、弹性势能可以相互转化并能举例说明。 (2)能解释一些有关动能、重力势能、弹性势能在内的转化的简单物理现象。 (3)常识性了解水能和风能的利用及其对我国社会主义建设的意义。 三. 分析: 1. 怎样理解“机械能”这个概念, 动能和势能统称为机械能，机械能是和物体的机械运动紧密联系的能量。 一个物体具有机械能时，可以现为只有动能，没有势能。例如，在水平地面上运动的物体，它的动能为200J，势能为零，这个物体的机械能为200J+0，等于200J。 一个物体具有机械能时，也可以表现为只有势能，没有动能。例如，被举在空中静止的杠铃，它的动能为零，重力势能为6000J，那么这个杠铃具有的机械能是6000J+0，为6000J。 一个物体既有动能，又有势能，它的机械能等于它的动能与势能之和，比如，在空中飞行的一颗子弹，它的动能是5000J，势能是150J，那么这颗子弹的机械能是5150J。 strengthen the sense of responsibility, work to solve the lack of decent occupation explain away, conduct problems. To establish the overall concept, eliminate departmentalism. Strict assessment and accountability, to solve the spiritual slack, nianqingpazhong, status quo, and other issues. To establish and perfect the muddle along Bureau staff conduct work regulations, standardize the behavior of personnel. 2. To strengthen the responsibility system. One is the in-depth study and implement the "Hunan provincial Party and government leading cadres Interim Provisions on the work safety of a pair of > (Hunan Office issued 2013 No. 5)," Hunan province safety supervision and management responsibilities of the provisions on the production (Hunan Zhengban made 2013 No. 4) And resolutely implement the safety production of the party with responsibility, a pair of responsibility. "Two is issued safety production administration and inspection to promote the responsibilities bear safety production supervision departments strictly and effectively assumed responsibility. The three is to establish risk self correction self reporting system for safety in production enterprises, promote the enterprises to implement the main responsibility for production safety is introduced. Four strengthen the county safety production supervision ability construction work, promote safe production responsibility to the grassroots. 3, strict accountability and target management. Adhere to the" who is in charge, who is responsible for the pipe industry must be safe, Guan Sheng production and operation must be safe, pipe business must control security "principle, the implementation of safety The production of "cure." stagnation supervision and leadership responsible system. The safety production of key towns, key enterprises and key problems, by the township government and the Department responsible for the stagnation led the lump sum, to tackle tough. To further increase the production safety index assessment, strictly implement the safety production of the "one vote veto" and the reward system, strengthen the safety incentive and restraint mechanism. (six) the implementation of the work force is not strong. The documents, meeting, long work arrangement, check and supervise the implementation of small, poor implementation of the system, the work is not effective. Some leading cadres sense of purpose, consciousness of the masses is not strong, the ruling " For the people "," the interests of the masses no matter "concept understanding is not in place. The specific work treats with the deployment, a few leading cadres complain that work is too complicated, too much responsibility, the pressure is too large, too much emphasis on the difficulty of the work, such as underground mines to avoid the disaster of" six systems "construction and construction of mechanical ventilation to file the form, forwarding arrangements work, no in-depth mining enterprises to promote the specific work, the increase in the number of files, but the effect is not good, not according to the actual situation of non coal mines in the county, to engage in" across the board ", and the quality 一切物体可以既具有动能又具有势能，也可以只具有动能或只具有势能。机械能大小的决定因素:质量、速度、高度、形变量。 2. 怎样分析物体动能和势能的变化, 物体的动能是由它的质量和速度两个因素决定的。 注意: (1)一个物体的动能与其质量的大小，运动的速度的大小有关。分析问时不能只考虑其中一个因素。 (2)对于一个物体而言，当速度不变时，质量越大其动能越大;当质量不变时，速度越大动能越大。改变物体的质量和速度都可以改变物体动能的大小。 (3)若物体做的是匀速运动，则表示该物体的速度大小不变，若该物体的质量又一定，则表明该物体的动能大小不变。 对于同一个物体来说，可能通过它的速度是否改变来判定它的动能是否变化。物体的速度不变，它的动能不变，物体的速度变大，它的动能增加;物体的速度变小，它的动能减少。物体的速度是零，它的动能也是零。 物体的重力势能是由它的质量和高度两个因素决定的，对于同一个物体来说，可以通过它的高度是否改变来判定它的重力势能是否变化。高度不变，物体的重力势能不变，高度增大，它的重力势能变大;高度减小，它的重力势能减小，初中阶段是以地面做为高度的计算起点，则地面上物体的重力势能为零。 3. 动能和势能相互转化的问题 (1)在动能和势能的相互转化过程中，机械能是否一定保持不变, 在动能和势能的转化过程中，若不考虑转化过程中的能量损失，则机械能的总量保持不变;在转化过程中若有能量损失(如克服阻力做功)或其他形式能的补充，则机械能的总量将发生变化。 在做滚摆的实验时，可以看到滚摆从高处旋转下降，越转越快，它的重力势能转化成了动能;到达最低点后，滚摆转而上升，它越转越慢，滚摆的动能又转化成重力势能。但滚摆不能回到原来的高度上，这表明滚摆的机械能减小了。这是因为滚摆与绳之间有摩擦，滚摆在运动中还受到了空气阻力，由于克服阻力做功，使滚摆的一部分机械能转化成其它能(内能)，它的机械能总量就减小了，不再保持不变。 (2)在分析物体的动能和势能的转化过程中，机械能是否守恒，应注意题设条件。如一小孩从光滑的斜面上滑下，速度越来越快，到斜面底端时:动能______，势能______，机械能总量______(选填“增大”、“减小”或“不变”)。 在这里“光滑”的即认为可以不考虑摩擦，因此在能量的转化中不考虑摩擦及能量的损失，小孩在下滑时，减少的势能全部转化成小孩的动能，机械能的总量不变。所以应是:动能增加，势能减少，机械能总量不变。 又如，一小孩从斜面上匀速下滑，到斜面底端时，动能______，势能______，机械能总量______。 strengthen the sense of responsibility, work to solve the lack of decent occupation explain away, conduct problems. To establish the overall concept, eliminate departmentalism. Strict assessment and accountability, to solve the spiritual slack, nianqingpazhong, status quo, and other issues. To establish and perfect the muddle along Bureau staff conduct work regulations, standardize the behavior of personnel. 2. To strengthen the responsibility system. One is the in-depth study and implement the "Hunan provincial Party and government leading cadres Interim Provisions on the work safety of a pair of > (Hunan Office issued 2013 No. 5)," Hunan province safety supervision and management responsibilities of the provisions on the production (Hunan Zhengban made 2013 No. 4) And resolutely implement the safety production of the party with responsibility, a pair of responsibility. "Two is issued safety production administration and inspection to promote the responsibilities bear safety production supervision departments strictly and effectively assumed responsibility. The three is to establish risk self correction self reporting system for safety in production enterprises, promote the enterprises to implement the main responsibility for production safety is introduced. Four strengthen the county safety production supervision ability construction work, promote safe production responsibility to the grassroots. 3, strict accountability and target management. Adhere to the" who is in charge, who is responsible for the pipe industry must be safe, Guan Sheng production and operation must be safe, pipe business must control security "principle, the implementation of safety The production of "cure." stagnation supervision and leadership responsible system. The safety production of key towns, key enterprises and key problems, by the township government and the Department responsible for the stagnation led the lump sum, to tackle tough. To further increase the production safety index assessment, strictly implement the safety production of the "one vote veto" and the reward system, strengthen the safety incentive and restraint mechanism. (six) the implementation of the work force is not strong. The documents, meeting, long work arrangement, check and supervise the implementation of small, poor implementation of the system, the work is not effective. Some leading cadres sense of purpose, consciousness of the masses is not strong, the ruling " For the people "," the interests of the masses no matter "concept understanding is not in place. The specific work treats with the deployment, a few leading cadres complain that work is too complicated, too much responsibility, the pressure is too large, too much emphasis on the difficulty of the work, such as underground mines to avoid the disaster of" six systems "construction and construction of mechanical ventilation to file the form, forwarding arrangements work, no in-depth mining enterprises to promote the specific work, the increase in the number of files, but the effect is not good, not according to the actual situation of non coal mines in the county, to engage in" across the board ", and the quality 由于小孩从斜面上“匀速”下滑，到底端时速度不变，因此动能不变，而由于高度降低，势能减少，因而机械能的总量减少。在题目中虽没明确说明摩擦的存在，但小孩从斜面上“匀速”下滑，就隐含了存在摩擦这个条件。因此，在转化中必然有一部分机械能消耗在克服阻力做功上，而引起机械能总量的减少。 【典型例题】 [例1] 一只乒乓球由高处静止下落撞击地板后又上升，在整个过程中，乒乓球机械能转化的情况是( ) A. 势能?动能?势能 B. 动能?势能?势能 C. 动能?势能?动能?势能?动能 D. 势能?动能?势能?动能?势能 分析:乒乓球在高处，由于被举高具有势能。在下落过程中，高度降低，速度增大，在撞击地面前，球的全部势能转化为动能。在撞击地板的一瞬间，由于球发生形变，球的动能转化为球的弹性势能。球在恢复形变的过程中，弹性势能又转化成动能，使球产生一个反方向的速度(如不考虑能的损失，则此速度与球撞击地板前的速度大小相同)，向上跳起。在上升的过程中，动能又逐渐转化成势能，直至动能为零。从下落到反跳的全过程中，经历的能量变化过程是:重力势能?动能?弹性势能?动能?重力势能。 解答:D。 说明:在解答同一物体的重力势能和动能之间的转化问题时，由于同一物体质量一定，所以重力势能和动能的变化，主要表现在离地面的高度与速度的大小变化。 [例2] 物体沿斜面匀速滑下时，它的( ) A. 动能增加，重力势能减少，机械能不变 B. 动能不变，重力势能不变，机械能不变 C. 动能不变，重力势能减少，机械能减少 D. 动能增加，重力势能减少，机械能减少 分析:注意物体是“匀速滑下”，说明物体运动的速度不变，所以动能不变。但随高度的降低，势能减少。因为机械能是动能与势能的统称，所以机械能由于动能不变而势能减少，因而也减少了。 解答:C。 说明:对于一个物体(质量一定)，它的动能是否变化就看它的速度是否变;它的重力势能是否变化就看它的高度是否变。 strengthen the sense of responsibility, work to solve the lack of decent occupation explain away, conduct problems. To establish the overall concept, eliminate departmentalism. Strict assessment and accountability, to solve the spiritual slack, nianqingpazhong, status quo, and other issues. To establish and perfect the muddle along Bureau staff conduct work regulations, standardize the behavior of personnel. 2. To strengthen the responsibility system. One is the in-depth study and implement the "Hunan provincial Party and government leading cadres Interim Provisions on the work safety of a pair of > (Hunan Office issued 2013 No. 5)," Hunan province safety supervision and management responsibilities of the provisions on the production (Hunan Zhengban made 2013 No. 4) And resolutely implement the safety production of the party with responsibility, a pair of responsibility. "Two is issued safety production administration and inspection to promote the responsibilities bear safety production supervision departments strictly and effectively assumed responsibility. The three is to establish risk self correction self reporting system for safety in production enterprises, promote the enterprises to implement the main responsibility for production safety is introduced. Four strengthen the county safety production supervision ability construction work, promote safe production responsibility to the grassroots. 3, strict accountability and target management. Adhere to the" who is in charge, who is responsible for the pipe industry must be safe, Guan Sheng production and operation must be safe, pipe business must control security "principle, the implementation of safety The production of "cure." stagnation supervision and leadership responsible system. The safety production of key towns, key enterprises and key problems, by the township government and the Department responsible for the stagnation led the lump sum, to tackle tough. To further increase the production safety index assessment, strictly implement the safety production of the "one vote veto" and the reward system, strengthen the safety incentive and restraint mechanism. (six) the implementation of the work force is not strong. The documents, meeting, long work arrangement, check and supervise the implementation of small, poor implementation of the system, the work is not effective. Some leading cadres sense of purpose, consciousness of the masses is not strong, the ruling " For the people "," the interests of the masses no matter "concept understanding is not in place. The specific work treats with the deployment, a few leading cadres complain that work is too complicated, too much responsibility, the pressure is too large, too much emphasis on the difficulty of the work, such as underground mines to avoid the disaster of" six systems "construction and construction of mechanical ventilation to file the form, forwarding arrangements work, no in-depth mining enterprises to promote the specific work, the increase in the number of files, but the effect is not good, not according to the actual situation of non coal mines in the county, to engage in" across the board ", and the quality [例3] 用一根不可伸长的细线，一端拴住一小球，另一端固定，如图所示。使小球偏离它静止时的位置O移至B点，然后释放，小球就沿弧摆动，小球从B?O?C?的过程中机械能发生怎样的转化, 分析:小球运动过程中，没有摩擦阻力，也没有外力对小球做功，只有动能和重力势能之间的转化。把小球从O点移到B点，是小球被举高的过程，因此小球在B点具有重力势能，但在B点速度为零，不具有动能。 小球从B?O运动时，高度逐渐减小，说明小球的重力势能逐渐减少;而小球的运动速度逐渐增大，说明小球的动能逐渐增大。在这个过程中，小球的重力势能转化成它的动能。 小球从O?C运动时，高度逐渐增加，说明小球的重力势能逐渐增加;而小球的运动速度逐渐减小至零，说明小球的动能逐渐减少至零。在这个过程中，小球的动能又转化成它的重力势能了。 解答: B—O重力势能减小，动能增加; O—C重力势能增加，动能减小; C—O同B—O; O—B同O—C。 [例4] 竖直向上抛起的石块，上升过程中，它的速度越来越小(空气的作用不计)，这是为什么, 分析:可以从力的角度和能的角度去考虑。 解答:从力的角度分析，在石块向上的过程中，石块受到的重力跟它的运动方向相反，因此使石块的速度越来越小。 从能的角度分析，在石块上升的过程中，它的势能增加，而势能是石块的动能转化来的，因此石块的动能减小，它的速度就会减小。 【模拟】 一. 判断题 strengthen the sense of responsibility, work to solve the lack of decent occupation explain away, conduct problems. To establish the overall concept, eliminate departmentalism. Strict assessment and accountability, to solve the spiritual slack, nianqingpazhong, status quo, and other issues. To establish and perfect the muddle along Bureau staff conduct work regulations, standardize the behavior of personnel. 2. To strengthen the responsibility system. One is the in-depth study and implement the "Hunan provincial Party and government leading cadres Interim Provisions on the work safety of a pair of > (Hunan Office issued 2013 No. 5)," Hunan province safety supervision and management responsibilities of the provisions on the production (Hunan Zhengban made 2013 No. 4) And resolutely implement the safety production of the party with responsibility, a pair of responsibility. "Two is issued safety production administration and inspection to promote the responsibilities bear safety production supervision departments strictly and effectively assumed responsibility. The three is to establish risk self correction self reporting system for safety in production enterprises, promote the enterprises to implement the main responsibility for production safety is introduced. Four strengthen the county safety production supervision ability construction work, promote safe production responsibility to the grassroots. 3, strict accountability and target management. Adhere to the" who is in charge, who is responsible for the pipe industry must be safe, Guan Sheng production and operation must be safe, pipe business must control security "principle, the implementation of safety The production of "cure." stagnation supervision and leadership responsible system. The safety production of key towns, key enterprises and key problems, by the township government and the Department responsible for the stagnation led the lump sum, to tackle tough. To further increase the production safety index assessment, strictly implement the safety production of the "one vote veto" and the reward system, strengthen the safety incentive and restraint mechanism. (six) the implementation of the work force is not strong. The documents, meeting, long work arrangement, check and supervise the implementation of small, poor implementation of the system, the work is not effective. Some leading cadres sense of purpose, consciousness of the masses is not strong, the ruling " For the people "," the interests of the masses no matter "concept understanding is not in place. The specific work treats with the deployment, a few leading cadres complain that work is too complicated, too much responsibility, the pressure is too large, too much emphasis on the difficulty of the work, such as underground mines to avoid the disaster of" six systems "construction and construction of mechanical ventilation to file the form, forwarding arrangements work, no in-depth mining enterprises to promote the specific work, the increase in the number of files, but the effect is not good, not according to the actual situation of non coal mines in the county, to engage in" across the board ", and the quality 1. 向上抛出的小球速度越来越小，因而动能越来越小。( ) 2. 一块大石头与一块小石头都被高举以后，大石头的势能一定比小石头势能大。( ) 3. 一个人乘在电梯里，当电梯匀速上升时，人的势能增加了，动能减少了。( ) 4. 小孩在荡秋千的过程中，一定是动能转化为势能。( ) 5. 悬挂在天花板上的吊灯处于静止状态，没有做功，所以也就没有能。( ) 6. 因为机械能可以相互转化，所以有动能的物体就一定有势能。( ) 7. 被抛出的铅球在空中运动时，因为没有对其他物体做功，所以它没有能。( ) 8. 一个人乘在飞机里，当飞机在匀速飞行时人的势能一定保持不变。( ) 9. 跳伞运动员在匀速下降过程中势能在减少，动能在增加。( ) 10. 所谓机械能就是机械所具有的能。( ) 二. 填空题 1. 人造地球卫星在近地点的速度比它在远地点的速度______，这是因为它在近地点的重力势能比它在远地点的重力势能______。从近地点到远地点的过程中，它的______能转化为______能。它在近地点的机械能______它在远地点的机械能(填“大于”、“小于”或“等于”)。 2. 弹簧门在推开后，能自动关闭，这是由于被推开后，弹簧被卷紧变形，具有______能，放手后，这个能转化为门的______能，使门被关上。 3. 物体在自由下落的过程中，物体的______减少，物体的______增加。 4. 如图1所示，摆球运动到最高点A点时，势能最______，动能为______;摆球从A点运动到B点的过程中，是______转化为______;在B点时势能为______，摆球的速度最______;当摆球运动到C点时，此时势能为______，动能为______。 5. 重锤从高处落下将桩打入土中，重锤在高处时具有______能，落下后转化为______能，在这个过程中______能不变。 strengthen the sense of responsibility, work to solve the lack of decent occupation explain away, conduct problems. To establish the overall concept, eliminate departmentalism. Strict assessment and accountability, to solve the spiritual slack, nianqingpazhong, status quo, and other issues. To establish and perfect the muddle along Bureau staff conduct work regulations, standardize the behavior of personnel. 2. To strengthen the responsibility system. One is the in-depth study and implement the "Hunan provincial Party and government leading cadres Interim Provisions on the work safety of a pair of > (Hunan Office issued 2013 No. 5)," Hunan province safety supervision and management responsibilities of the provisions on the production (Hunan Zhengban made 2013 No. 4) And resolutely implement the safety production of the party with responsibility, a pair of responsibility. "Two is issued safety production administration and inspection to promote the responsibilities bear safety production supervision departments strictly and effectively assumed responsibility. The three is to establish risk self correction self reporting system for safety in production enterprises, promote the enterprises to implement the main responsibility for production safety is introduced. Four strengthen the county safety production supervision ability construction work, promote safe production responsibility to the grassroots. 3, strict accountability and target management. Adhere to the" who is in charge, who is responsible for the pipe industry must be safe, Guan Sheng production and operation must be safe, pipe business must control security "principle, the implementation of safety The production of "cure." stagnation supervision and leadership responsible system. The safety production of key towns, key enterprises and key problems, by the township government and the Department responsible for the stagnation led the lump sum, to tackle tough. To further increase the production safety index assessment, strictly implement the safety production of the "one vote veto" and the reward system, strengthen the safety incentive and restraint mechanism. (six) the implementation of the work force is not strong. The documents, meeting, long work arrangement, check and supervise the implementation of small, poor implementation of the system, the work is not effective. Some leading cadres sense of purpose, consciousness of the masses is not strong, the ruling " For the people "," the interests of the masses no matter "concept understanding is not in place. The specific work treats with the deployment, a few leading cadres complain that work is too complicated, too much responsibility, the pressure is too large, too much emphasis on the difficulty of the work, such as underground mines to avoid the disaster of" six systems "construction and construction of mechanical ventilation to file the form, forwarding arrangements work, no in-depth mining enterprises to promote the specific work, the increase in the number of files, but the effect is not good, not according to the actual situation of non coal mines in the county, to engage in" across the board ", and the quality 6. 如图2所示，让摆在最高点A点时，势能最______，动能为______;从A滚动到B点时，是______转化为______，此时既有______又有______;从B点滚动到最低点C点时，势能最______，动能最______。 图2 7. 在空气中匀速下落的降落伞，它的动能______，重力势能______，机械能______(填“增大”、“减小”、“不变”) 8. 小孩在打秋千时，别人把他推高一下后，他就来回悠荡，秋千由高处荡回再向另一侧升高的过程中，是由______能转化为______能，再由______能转化为______能的过程。 三. 选择题 1. 如图3所示，同一木块沿AB，AC，AD三个光滑的斜面(高度相等)滑下的过程中，重力势能都转化成动能，滑至底端时，动能较大的是( ) A. 沿AB滑下的木块 B. 沿AC滑下的木块 C. 沿AD滑下的木块 D. 它们的动能一样大 图3 2. 风力发电是( ) A. 将风变成电 B. 将风的势能转变为电能 C. 将风的动能转变为电能 D. 将风的动能转变为势能 3. 下列各个过程中，属于动能转化为势能的是( ) strengthen the sense of responsibility, work to solve the lack of decent occupation explain away, conduct problems. To establish the overall concept, eliminate departmentalism. Strict assessment and accountability, to solve the spiritual slack, nianqingpazhong, status quo, and other issues. To establish and perfect the muddle along Bureau staff conduct work regulations, standardize the behavior of personnel. 2. To strengthen the responsibility system. One is the in-depth study and implement the "Hunan provincial Party and government leading cadres Interim Provisions on the work safety of a pair of > (Hunan Office issued 2013 No. 5)," Hunan province safety supervision and management responsibilities of the provisions on the production (Hunan Zhengban made 2013 No. 4) And resolutely implement the safety production of the party with responsibility, a pair of responsibility. "Two is issued safety production administration and inspection to promote the responsibilities bear safety production supervision departments strictly and effectively assumed responsibility. The three is to establish risk self correction self reporting system for safety in production enterprises, promote the enterprises to implement the main responsibility for production safety is introduced. Four strengthen the county safety production supervision ability construction work, promote safe production responsibility to the grassroots. 3, strict accountability and target management. Adhere to the" who is in charge, who is responsible for the pipe industry must be safe, Guan Sheng production and operation must be safe, pipe business must control security "principle, the implementation of safety The production of "cure." stagnation supervision and leadership responsible system. The safety production of key towns, key enterprises and key problems, by the township government and the Department responsible for the stagnation led the lump sum, to tackle tough. To further increase the production safety index assessment, strictly implement the safety production of the "one vote veto" and the reward system, strengthen the safety incentive and restraint mechanism. (six) the implementation of the work force is not strong. The documents, meeting, long work arrangement, check and supervise the implementation of small, poor implementation of the system, the work is not effective. Some leading cadres sense of purpose, consciousness of the masses is not strong, the ruling " For the people "," the interests of the masses no matter "concept understanding is not in place. The specific work treats with the deployment, a few leading cadres complain that work is too complicated, too much responsibility, the pressure is too large, too much emphasis on the difficulty of the work, such as underground mines to avoid the disaster of" six systems "construction and construction of mechanical ventilation to file the form, forwarding arrangements work, no in-depth mining enterprises to promote the specific work, the increase in the number of files, but the effect is not good, not according to the actual situation of non coal mines in the county, to engage in" across the board ", and the quality A. 钟表的发条使指针转动 B. 冰雹从空中落下 C. 篮球从地上弹起后上升过程 D. 大型塔式起重机将货物匀速吊起 4. 如图4所示，A、B、C是三个高度相同而倾角不同的光滑斜面，让质量相同的小球沿斜面从顶端运动到底端，比较小球滚到底端时速度大( ) 图4 A. 在A的速度最大 B. 在C点的速度最大 C. 在A、B、C三点速度相同 D. 无法判断 5. 如图5所示，小球从离地h的高度沿着光滑的轨道滑下，使小球滑到光滑的离心轨道顶端A而不下落，此时( ) 图5 A. 小球既有势能，又有动能 B. 小球只有势能，没有动能 C. 小球只有动能，没有势能 D. 以上说法都不正确 6. 一个人乘在电梯里，当电梯匀速上升时，人的( ) A. 势能增加，动能减少 B. 势能减少，动能不变 C. 势能增加，动能增加 D. 势能增加，动能不变 7. 如图6所示，让一个小球分别沿着光滑的斜面BA或BC滚下，比较小球滚到A处与C处的速度大小是( ) strengthen the sense of responsibility, work to solve the lack of decent occupation explain away, conduct problems. To establish the overall concept, eliminate departmentalism. Strict assessment and accountability, to solve the spiritual slack, nianqingpazhong, status quo, and other issues. To establish and perfect the muddle along Bureau staff conduct work regulations, standardize the behavior of personnel. 2. To strengthen the responsibility system. One is the in-depth study and implement the "Hunan provincial Party and government leading cadres Interim Provisions on the work safety of a pair of > (Hunan Office issued 2013 No. 5)," Hunan province safety supervision and management responsibilities of the provisions on the production (Hunan Zhengban made 2013 No. 4) And resolutely implement the safety production of the party with responsibility, a pair of responsibility. "Two is issued safety production administration and inspection to promote the responsibilities bear safety production supervision departments strictly and effectively assumed responsibility. The three is to establish risk self correction self reporting system for safety in production enterprises, promote the enterprises to implement the main responsibility for production safety is introduced. Four strengthen the county safety production supervision ability construction work, promote safe production responsibility to the grassroots. 3, strict accountability and target management. Adhere to the" who is in charge, who is responsible for the pipe industry must be safe, Guan Sheng production and operation must be safe, pipe business must control security "principle, the implementation of safety The production of "cure." stagnation supervision and leadership responsible system. The safety production of key towns, key enterprises and key problems, by the township government and the Department responsible for the stagnation led the lump sum, to tackle tough. To further increase the production safety index assessment, strictly implement the safety production of the "one vote veto" and the reward system, strengthen the safety incentive and restraint mechanism. (six) the implementation of the work force is not strong. The documents, meeting, long work arrangement, check and supervise the implementation of small, poor implementation of the system, the work is not effective. Some leading cadres sense of purpose, consciousness of the masses is not strong, the ruling " For the people "," the interests of the masses no matter "concept understanding is not in place. The specific work treats with the deployment, a few leading cadres complain that work is too complicated, too much responsibility, the pressure is too large, too much emphasis on the difficulty of the work, such as underground mines to avoid the disaster of" six systems "construction and construction of mechanical ventilation to file the form, forwarding arrangements work, no in-depth mining enterprises to promote the specific work, the increase in the number of files, but the effect is not good, not according to the actual situation of non coal mines in the county, to engage in" across the board ", and the quality 图6 A. 小球在A点的速度大于在C点的速度 B. 小球在A点的速度等于在C点的速度 C. 小球在A点的速度小于在C点的速度 D. 无法判定 8. 把玩具汽车的发条旋紧后，它能在桌面上水平前进。这是因为( ) A. 发条的动能转化为小车的动能 B. 发条的弹性势能转化为小车的动能 C. 由于能量守恒，所以小车会一直运动下去 D. 到最后小车会停止，这说明能量不守恒 9. 如图7所示，AB为光滑斜面，BC为粗糙而足够长的水平面。物体m从斜面的顶端A点由静止开始下滑，则在BC水平面上物体的( ) 图7 A. 动能减少，势能增加 B. 势能减少，动能增加 C. 动能增加，势能不变 D. 动能减小，势能不变 10. 下列过程中，动能转化成势能的是( ) A. 将一块石头向上抛去 B. 张开的弓把箭射出去 C. 雨滴自房顶落下 D. 山坡上滚下的大石头 11. 做功是需要消耗能量的，在以下各种情况下，消耗势能转化成动能的是( ) A. 箭能射穿靶心 B. 上发条的钟在走动 C. 风吹使风车转动 D. 电风扇在转动 12. 机械手表中指针的走动是利用了( ) strengthen the sense of responsibility, work to solve the lack of decent occupation explain away, conduct problems. To establish the overall concept, eliminate departmentalism. Strict assessment and accountability, to solve the spiritual slack, nianqingpazhong, status quo, and other issues. To establish and perfect the muddle along Bureau staff conduct work regulations, standardize the behavior of personnel. 2. To strengthen the responsibility system. One is the in-depth study and implement the "Hunan provincial Party and government leading cadres Interim Provisions on the work safety of a pair of > (Hunan Office issued 2013 No. 5)," Hunan province safety supervision and management responsibilities of the provisions on the production (Hunan Zhengban made 2013 No. 4) And resolutely implement the safety production of the party with responsibility, a pair of responsibility. "Two is issued safety production administration and inspection to promote the responsibilities bear safety production supervision departments strictly and effectively assumed responsibility. The three is to establish risk self correction self reporting system for safety in production enterprises, promote the enterprises to implement the main responsibility for production safety is introduced. Four strengthen the county safety production supervision ability construction work, promote safe production responsibility to the grassroots. 3, strict accountability and target management. Adhere to the" who is in charge, who is responsible for the pipe industry must be safe, Guan Sheng production and operation must be safe, pipe business must control security "principle, the implementation of safety The production of "cure." stagnation supervision and leadership responsible system. The safety production of key towns, key enterprises and key problems, by the township government and the Department responsible for the stagnation led the lump sum, to tackle tough. To further increase the production safety index assessment, strictly implement the safety production of the "one vote veto" and the reward system, strengthen the safety incentive and restraint mechanism. (six) the implementation of the work force is not strong. The documents, meeting, long work arrangement, check and supervise the implementation of small, poor implementation of the system, the work is not effective. Some leading cadres sense of purpose, consciousness of the masses is not strong, the ruling " For the people "," the interests of the masses no matter "concept understanding is not in place. The specific work treats with the deployment, a few leading cadres complain that work is too complicated, too much responsibility, the pressure is too large, too much emphasis on the difficulty of the work, such as underground mines to avoid the disaster of" six systems "construction and construction of mechanical ventilation to file the form, forwarding arrangements work, no in-depth mining enterprises to promote the specific work, the increase in the number of files, but the effect is not good, not according to the actual situation of non coal mines in the county, to engage in" across the board ", and the quality A. 弹性势能转化为动能 B. 动能转化为弹性势能 C. 重力势能转化为动能 D. 以上说法都不对 四. 问答题 1. 从玩具店买来的橡塑小球掉在地上(水泥地)再弹起来，试分析整个过程中机械能转化的情况。 2. 骑自行车时，在上坡前往往要加紧蹬几下，为什么要这样做, 五. 实验题 如图8所示，一小钢球从斜面滚下，滚到水平面上后又被一弹簧片把钢球弹了回去，指出下面几个过程中小球的能量转化关系: (1)小球由A?B是______能转化为______能; (2)小球由B?C是______能转化为______能; (3)小球由C?D是______能转化为______能; 图8 strengthen the sense of responsibility, work to solve the lack of decent occupation explain away, conduct problems. To establish the overall concept, eliminate departmentalism. Strict assessment and accountability, to solve the spiritual slack, nianqingpazhong, status quo, and other issues. To establish and perfect the muddle along Bureau staff conduct work regulations, standardize the behavior of personnel. 2. To strengthen the responsibility system. One is the in-depth study and implement the "Hunan provincial Party and government leading cadres Interim Provisions on the work safety of a pair of > (Hunan Office issued 2013 No. 5)," Hunan province safety supervision and management responsibilities of the provisions on the production (Hunan Zhengban made 2013 No. 4) And resolutely implement the safety production of the party with responsibility, a pair of responsibility. "Two is issued safety production administration and inspection to promote the responsibilities bear safety production supervision departments strictly and effectively assumed responsibility. The three is to establish risk self correction self reporting system for safety in production enterprises, promote the enterprises to implement the main responsibility for production safety is introduced. Four strengthen the county safety production supervision ability construction work, promote safe production responsibility to the grassroots. 3, strict accountability and target management. Adhere to the" who is in charge, who is responsible for the pipe industry must be safe, Guan Sheng production and operation must be safe, pipe business must control security "principle, the implementation of safety The production of "cure." stagnation supervision and leadership responsible system. The safety production of key towns, key enterprises and key problems, by the township government and the Department responsible for the stagnation led the lump sum, to tackle tough. To further increase the production safety index assessment, strictly implement the safety production of the "one vote veto" and the reward system, strengthen the safety incentive and restraint mechanism. (six) the implementation of the work force is not strong. The documents, meeting, long work arrangement, check and supervise the implementation of small, poor implementation of the system, the work is not effective. Some leading cadres sense of purpose, consciousness of the masses is not strong, the ruling " For the people "," the interests of the masses no matter "concept understanding is not in place. The specific work treats with the deployment, a few leading cadres complain that work is too complicated, too much responsibility, the pressure is too large, too much emphasis on the difficulty of the work, such as underground mines to avoid the disaster of" six systems "construction and construction of mechanical ventilation to file the form, forwarding arrangements work, no in-depth mining enterprises to promote the specific work, the increase in the number of files, but the effect is not good, not according to the actual situation of non coal mines in the county, to engage in" across the board ", and the quality strengthen the sense of responsibility, work to solve the lack of decent occupation explain away, conduct problems. To establish the overall concept, eliminate departmentalism. Strict assessment and accountability, to solve the spiritual slack, nianqingpazhong, status quo, and other issues. To establish and perfect the muddle along Bureau staff conduct work regulations, standardize the behavior of personnel. 2. To strengthen the responsibility system. One is the in-depth study and implement the "Hunan provincial Party and government leading cadres Interim Provisions on the work safety of a pair of > (Hunan Office issued 2013 No. 5)," Hunan province safety supervision and management responsibilities of the provisions on the production (Hunan Zhengban made 2013 No. 4) And resolutely implement the safety production of the party with responsibility, a pair of responsibility. "Two is issued safety production administration and inspection to promote the responsibilities bear safety production supervision departments strictly and effectively assumed responsibility. The three is to establish risk self correction self reporting system for safety in production enterprises, promote the enterprises to implement the main responsibility for production safety is introduced. Four strengthen the county safety production supervision ability construction work, promote safe production responsibility to the grassroots. 3, strict accountability and target management. Adhere to the" who is in charge, who is responsible for the pipe industry must be safe, Guan Sheng production and operation must be safe, pipe business must control security "principle, the implementation of safety The production of "cure." stagnation supervision and leadership responsible system. The safety production of key towns, key enterprises and key problems, by the township government and the Department responsible for the stagnation led the lump sum, to tackle tough. To further increase the production safety index assessment, strictly implement the safety production of the "one vote veto" and the reward system, strengthen the safety incentive and restraint mechanism. (six) the implementation of the work force is not strong. The documents, meeting, long work arrangement, check and supervise the implementation of small, poor implementation of the system, the work is not effective. Some leading cadres sense of purpose, consciousness of the masses is not strong, the ruling " For the people "," the interests of the masses no matter "concept understanding is not in place. The specific work treats with the deployment, a few leading cadres complain that work is too complicated, too much responsibility, the pressure is too large, too much emphasis on the difficulty of the work, such as underground mines to avoid the disaster of" six systems "construction and construction of mechanical ventilation to file the form, forwarding arrangements work, no in-depth mining enterprises to promote the specific work, the increase in the number of files, but the effect is not good, not according to the actual situation of non coal mines in the county, to engage in" across the board ", and the quality