2011届高考物理第一轮经典模型检测试题19绳子、弹簧和杆产生的弹力特点

2011届高考物理第一轮经典模型检测试题19绳子、弹簧和杆产生的弹力特点 绳子、弹簧和杆产生的弹力特点 模型特点: 1. 轻绳 (1)轻绳模型的特点 “绳”在物理学上是个绝对柔软的物体，它只产生拉力(张力)，绳的拉力沿着绳的方向并 指向绳的收缩方向。它不能产生支持作用。 它的质量可忽略不计，轻绳是软的，不能产生侧向力，只能产生沿着绳子方向的力。它的劲 度系数非常大，以至于认为在受力时形变极微小，看作不可伸长。 (2)轻绳模型的规律 ?轻绳各处受力相等，且拉力方向沿着绳子; ?轻绳不能伸长; ?用轻绳连接的系统通过轻绳的碰撞、撞击时，系统的机械能有损失; ?轻绳的弹力会发生突变。 2. 轻杆 (l)轻杆模型的特点 轻杆的质量可忽略不计，轻杆是硬的，能产生侧向力，它的劲度系数非常大，以至于认为在 受力时形变极微小，看作不可伸长或压缩。 (2)轻杆模型的规律 ?轻杆各处受力相等，其力的方向不一定沿着杆的方向; ?轻杆不能伸长或压缩; ?轻杆受到的弹力的方式有拉力或压力。 3. 轻弹簧 (1)轻弹簧模型的特点 轻弹簧可以被压缩或拉伸，其弹力的大小与弹簧的伸长量或缩短量有关。 (2)轻弹簧的规律 ?轻弹簧各处受力相等，其方向与弹簧形变的方向相反; 第1页 that construction site clean, consciously maintain sanitation. (4) ensure the safety of materials and semi-finished products. 8. quality assessment, data compilation: buried, belongs to the concealed works construction, therefore its quality inspection must be carried out according to acceptance of concealed work-related. Mainly in the following aspects: (1) acceptance of positioning is accurate. (2) is fixed securely. (3) tightening compliance requirements. (4) have an impact on other projects. (5) the material used is eligible. (6) complete information has been collected. Documentation: should follow construction progress at any time finishing self acceptance, signature acceptance after the representatives of the party were invited. Requirements: (1) covert acceptance is thea the company's situation, familiar with the period schedule master plan, construction with water, power supply, vertical transportation, gondola of external scaffolding or construction. (2) technical data preparation: first drawings to prepare the drawings to be fully familiar with, and does not have difficult places to ask out clearly understood, you also need to prepare acceptance of the Atlas, the quality standards, safety index, all the forms used and the acceptance required for the works, and more. (3) tools, implements preparation: supply planning against the required tools, appliances, specific to the type, quantity, supply time, also plans to supply, warehouse, and other departments, common tools and appliances. (4) materials: according to the drawings and engineering, detailed material supply meter ... (2) preparations into people, and clear accountability to specific persons. (3) implementation of collaboration and cooperation with construction companies. 2.15 embedded part installation (early works with civil engineering completed) 1. Note: buried is one of the curtain wall with main structure connecting structure, embedded quality directly affects the production, installation of curtain wall and the main structure of the connections. Its installation has a direct impact on the degree of precision of curtain wall construction accuracy and surface quality is good or bad. So the first job as a curtain wall installation, buried both for its manufacture and installation are directly affects the entire curtain wall construction, installation, and an important factor in the overall effect. 2. material specifications: the embedded parts. 3. basic operation: (1) familiar with the drawings: installation personnel after receivingtypeset by the owners ' consent before they can purchase and order under the program, each stone must use the same background, the same pattern, size error in 0.5mm stone. Air infiltration properties, stone curtain wall wind pressure rainwater leakage in distortion performance, performance and energy-saving performance in front of the construction should be in accordance with the construction plan of the specification and the file size in the appropriate authority inspection departments qualified testing. Stone used steel keel, installation job main including following steps: 2.1 construction Qian prepared 2.2 pre buried pieces processing 2.3 measurement and the measurement results figure draws 2.4 vertical box positioning put line 2.5 turned received pieces installation 2.6 vertical box installation 2.7 vertical box correction and acceptance 2.8 layer high and the cross box measurement positioning and put line 2.9 cross box installation 2.10 installation 2.11 stone plate installation 2.12 sealed rubber injection 2.13 clean ending 2.14 construction Qian prepared 1. Description Project Manager required for the duration of the project schedule, technical information, tools, machinery, apparatus, materials, personnel, temporary facilities ready. 2. the scope of previous construction (1) project outline: to understand the site profiles, familiar with the construction and supervision of party ?弹力的大小为F=kx，其中k为弹簧的劲度系数，x为弹簧的伸长量或缩短量; ?弹簧的弹力不会发生突变。 案例探究: 【案例1】如图所示，一质量为m的物体系于长度分别为L、L的两根细绳OA、OB上，12 0B一端悬挂在天花板上，与竖直方向夹角为θ，OA水平拉直，物体处于平衡状态，现在将OA剪断，求剪断瞬间物体的加速度，若将绳OB换为长度为L的弹簧，结果又如何, 2 B B θ O O A A 甲 乙 与解答: 为研究方便，我们两种情况对比分析。 )剪断前，两种情况小球受力一样，分别如图(1)、(2)所示，利用平衡条件，则 (1 mg与F的合力与F大小相等，方向相反，可以解得F=mgtgθ。 211 B F2θ O A F 1 F 1 (1) mg (2)剪断后瞬间，绳OA产生的拉力F消失， 1 对绳来说，其伸长量很微小，可以忽略不计，不需要形变恢复时间，因此，绳子中的张力也立即发生变化，这时F将发生瞬时变化，mg与F的合力将不再沿22 水平方向，而是由于小球下一时刻做单摆运动沿圆弧的 F2F 2切线方向，与绳垂直，如图(3)所示，F=mgsinθ，合 F 所以a=gsinθ。 1F 合 对弹簧来说，其伸长量大，形变恢复需要较长时mg mg (3) (4) that construction site clean, consciously maintain sanitation. (4) ensure the safety of materials and semi-finished products. 8. quality assessment, data compilation: buried, belongs to the concealed works construction, therefore its quality inspection must be carried out according to acceptance of concealed work-related. Mainly in the following aspects: (1) acceptance of positioning is accurate. (2) is fixed securely. (3) tightening compliance requirements. (4) have an impact on other projects. (5) the material used is eligible. (6) complete information has been collected. Documentation: should follow construction progress at any time finishing self acceptance, signature acceptance after the representatives of the party were invited. Requirements: (1) covert acceptance is thea the company's situation, familiar with the period schedule master plan, construction with water, power supply, vertical transportation, gondola of external scaffolding or construction. (2) technical data preparation: first drawings to prepare the drawings to be fully familiar with, and does not have difficult places to ask out clearly understood, you also need to prepare acceptance of the Atlas, the quality standards, safety index, all the forms used and the acceptance required for the works, and more. (3) tools, implements preparation: supply planning against the required tools, appliances, specific to the type, quantity, supply time, also plans to supply, warehouse, and other departments, common tools and appliances. (4) materials: according to the drawings and engineering, detailed material supply meter ... (2) preparations into people, and clear accountability to specific persons. (3) implementation of collaboration and cooperation with construction companies. 2.15 embedded part installation (early works with civil engineering completed) 1. Note: buried is one of the curtain wall with main structure connecting structure, embedded quality directly affects the production, installation of curtain wall and the main structure of the connections. Its installation has a direct impact on the degree of precision of curtain wall construction accuracy and surface quality is good or bad. So the first job as a curtain wall installation, buried both for its manufacture and installation are directly affects the entire curtain wall construction, installation, and an important factor in the overall effect. 2. material specifications: the embedded parts. 3. basic operation: (1) familiar with the drawings: installation personnel after receivingtypeset by the owners ' consent before they can purchase and order under the program, each stone must use the same background, the same pattern, size error in 0.5mm stone. Air infiltration properties, stone curtain wall wind pressure rainwater leakage in distortion performance, performance and energy-saving performance in front of the construction should be in accordance with the construction plan of the specification and the file size in the appropriate authority inspection departments qualified testing. Stone used steel keel, installation job main including following steps: 2.1 construction Qian prepared 2.2 pre buried pieces processing 2.3 measurement and the measurement results figure draws 2.4 vertical box positioning put line 2.5 turned received pieces installation 2.6 vertical box installation 2.7 vertical box correction and acceptance 2.8 layer high and the cross box measurement positioning and put line 2.9 cross box installation 2.10 installation 2.11 stone plate installation 2.12 sealed rubber injection 2.13 clean ending 2.14 construction Qian prepared 1. Description Project Manager required for the duration of the project schedule, technical information, tools, machinery, apparatus, materials, personnel, temporary facilities ready. 2. the scope of previous construction (1) project outline: to understand the site profiles, familiar with the construction and supervision of party 间，认为弹簧的长度还没有发生变化。这时F不发生变 2 第2页 化，故mg与F的合力仍然保持不变，与F大小相等，方向相反，如图(4)所示，21 所以F= F=mgstgθ， 合1 a=gstgθ。 【案例2】一根细绳，长度为L，一端系一个质量为m的小球，在竖直面内做圆周运动，求小球通过最高点时的速度至少是多少,若将绳换为一根匀质细杆，结果又如何, 分析与解答: v (1)对绳来说，是个柔软的物体， F mg 它只产生拉力，不能产生支持作用， 小球在最高点时， (1) 弹力只可能向下，如图(1)所示。 2mvF，mg,,mg这种情况下有 L 即，否则不能通过最高点。 v,gL (2)对细杆来说，是坚硬的物体，它的弹力既可能向上又可能向下，速度大小v可以取任意值。 可以进一步讨论: ?当杆对小球的作用力为向下的拉力时，如图(2)所示: 2mvF+mg=,mg 所以 v, gLL ?当杆对小球的作用力为向上的支持力时，如图(3)所示: 2mvmg,F=,mg 所以 v, gLL 当N=mg时，v可以等于零。 ?当弹力恰好为零时，如图(4)所示: 2mvmg= 所以 v=gL L that construction site clean, consciously maintain sanitation. (4) ensure the safety of materials and semi-finished products. 8. quality assessment, data compilation: buried, belongs to the concealed works construction, therefore its quality inspection must be carried out according to acceptance of concealed work-related. Mainly in the following aspects: (1) acceptance of positioning is accurate. (2) is fixed securely. (3) tightening compliance requirements. (4) have an impact on other projects. (5) the material used is eligible. (6) complete information has been collected. Documentation: should follow construction progress at any time finishing self acceptance, signature acceptance after the representatives of the party were invited. Requirements: (1) covert acceptance is thea the company's situation, familiar with the period schedule master plan, construction with water, power supply, vertical transportation, gondola of external scaffolding or construction. (2) technical data preparation: first drawings to prepare the drawings to be fully familiar with, and does not have difficult places to ask out clearly understood, you also need to prepare acceptance of the Atlas, the quality standards, safety index, all the forms used and the acceptance required for the works, and more. (3) tools, implements preparation: supply planning against the required tools, appliances, specific to the type, quantity, supply time, also plans to supply, warehouse, and other departments, common tools and appliances. (4) materials: according to the drawings and engineering, detailed material supply meter ... (2) preparations into people, and clear accountability to specific persons. (3) implementation of collaboration and cooperation with construction companies. 2.15 embedded part installation (early works with civil engineering completed) 1. Note: buried is one of the curtain wall with main structure connecting structure, embedded quality directly affects the production, installation of curtain wall and the main structure of the connections. Its installation has a direct impact on the degree of precision of curtain wall construction accuracy and surface quality is good or bad. So the first job as a curtain wall installation, buried both for its manufacture and installation are directly affects the entire curtain wall construction, installation, and an important factor in the overall effect. 2. material specifications: the embedded parts. 3. basic operation: (1) familiar with the drawings: installation personnel after receivingtypeset by the owners ' consent before they can purchase and order under the program, each stone must use the same background, the same pattern, size error in 0.5mm stone. Air infiltration properties, stone curtain wall wind pressure rainwater leakage in distortion performance, performance and energy-saving performance in front of the construction should be in accordance with the construction plan of the specification and the file size in the appropriate authority inspection departments qualified testing. Stone used steel keel, installation job main including following steps: 2.1 construction Qian prepared 2.2 pre buried pieces processing 2.3 measurement and the measurement results figure draws 2.4 vertical box positioning put line 2.5 turned received pieces installation 2.6 vertical box installation 2.7 vertical box correction and acceptance 2.8 layer high and the cross box measurement positioning and put line 2.9 cross box installation 2.10 installation 2.11 stone plate installation 2.12 sealed rubber injection 2.13 clean ending 2.14 construction Qian prepared 1. Description Project Manager required for the duration of the project schedule, technical information, tools, machinery, apparatus, materials, personnel, temporary facilities ready. 2. the scope of previous construction (1) project outline: to understand the site profiles, familiar with the construction and supervision of party F v 第3页 v F mg mg mg (3) (2) (4) 【案例3】如图所示，小车上固定一弯折硬杆ABC,C端固B α 定质量为m的小球，已知α=30?恒定。当小车水平向左以C v=0.5m/s的速度匀速运动时，BC杆对小球的作用力的大小A 是 ，方向是 ;当小车水平向左以a=g的加速度 作匀加速运动时，BC杆对小球的作用力的大小是 ，方向是 。 分析与解答: 对细杆来说，是坚硬的物体，可以产生与杆垂直的横向的力，也可以产生与杆任何夹角的弹力 (1)当小车水平向左以v=0.5m/s的速度匀速运动时，由平衡条件，细杆对小球的力必定与重力等大反向，如图(1)所示。 (2)当小车水平向左以a=g的加速度作匀加速运动时，小球所受合力F=mg沿水平方合 02向，则小球受细杆的弹力N=mg，与水平方向夹角为45，如图(2)所示。 B N N C C F=mg 合 A mg A mg (1) (2) that construction site clean, consciously maintain sanitation. (4) ensure the safety of materials and semi-finished products. 8. quality assessment, data compilation: buried, belongs to the concealed works construction, therefore its quality inspection must be carried out according to acceptance of concealed work-related. Mainly in the following aspects: (1) acceptance of positioning is accurate. (2) is fixed securely. (3) tightening compliance requirements. (4) have an impact on other projects. (5) the material used is eligible. (6) complete information has been collected. Documentation: should follow construction progress at any time finishing self acceptance, signature acceptance after the representatives of the party were invited. Requirements: (1) covert acceptance is thea the company's situation, familiar with the period schedule master plan, construction with water, power supply, vertical transportation, gondola of external scaffolding or construction. (2) technical data preparation: first drawings to prepare the drawings to be fully familiar with, and does not have difficult places to ask out clearly understood, you also need to prepare acceptance of the Atlas, the quality standards, safety index, all the forms used and the acceptance required for the works, and more. (3) tools, implements preparation: supply planning against the required tools, appliances, specific to the type, quantity, supply time, also plans to supply, warehouse, and other departments, common tools and appliances. (4) materials: according to the drawings and engineering, detailed material supply meter ... (2) preparations into people, and clear accountability to specific persons. (3) implementation of collaboration and cooperation with construction companies. 2.15 embedded part installation (early works with civil engineering completed) 1. Note: buried is one of the curtain wall with main structure connecting structure, embedded quality directly affects the production, installation of curtain wall and the main structure of the connections. Its installation has a direct impact on the degree of precision of curtain wall construction accuracy and surface quality is good or bad. So the first job as a curtain wall installation, buried both for its manufacture and installation are directly affects the entire curtain wall construction, installation, and an important factor in the overall effect. 2. material specifications: the embedded parts. 3. basic operation: (1) familiar with the drawings: installation personnel after receivingtypeset by the owners ' consent before they can purchase and order under the program, each stone must use the same background, the same pattern, size error in 0.5mm stone. Air infiltration properties, stone curtain wall wind pressure rainwater leakage in distortion performance, performance and energy-saving performance in front of the construction should be in accordance with the construction plan of the specification and the file size in the appropriate authority inspection departments qualified testing. Stone used steel keel, installation job main including following steps: 2.1 construction Qian prepared 2.2 pre buried pieces processing 2.3 measurement and the measurement results figure draws 2.4 vertical box positioning put line 2.5 turned received pieces installation 2.6 vertical box installation 2.7 vertical box correction and acceptance 2.8 layer high and the cross box measurement positioning and put line 2.9 cross box installation 2.10 installation 2.11 stone plate installation 2.12 sealed rubber injection 2.13 clean ending 2.14 construction Qian prepared 1. Description Project Manager required for the duration of the project schedule, technical information, tools, machinery, apparatus, materials, personnel, temporary facilities ready. 2. the scope of previous construction (1) project outline: to understand the site profiles, familiar with the construction and supervision of party 第4页 精品练习: 1.如图所示，有一质量为m的小球用轻绳悬挂于小车顶部，小车静止或匀速直线运动时，求绳子对小球作用力的大小和方向。 2. 如图所示，小车上有一弯折轻杆，杆下端固定一质量为m的小球。当小车处于静止或匀速直线运动状态时，求杆对球的作用力的大小和方向。 3. 如图所示，一质量为m的小球用轻绳悬挂在小车顶部，小车向左以加速度a做匀加速直线运动时，求轻绳对小球的作用力的大小和方向。 4. 若将上题中的轻绳换成固定的轻杆，当小车向左以加速度a做匀加速直线运动时， 求杆对球的作用力的大小及方向。 5. 如图6所示，小球在细线OB和水平细线AB的作用下而处于静止状态，则在剪断水平细线的瞬间，小球的加速度多大,方向如何, 6. 如图9所示，一轻质弹簧和一根细线共同提住一个质量为m的小球，平衡时细线是水平的，弹簧与竖直方向的夹角是，若突然剪断细线，则在剪断的瞬间，弹簧拉力的大小是__________，小球加速度与竖直方向夹角等于_________。 that construction site clean, consciously maintain sanitation. (4) ensure the safety of materials and semi-finished products. 8. quality assessment, data compilation: buried, belongs to the concealed works construction, therefore its quality inspection must be carried out according to acceptance of concealed work-related. Mainly in the following aspects: (1) acceptance of positioning is accurate. (2) is fixed securely. (3) tightening compliance requirements. (4) have an impact on other projects. (5) the material used is eligible. (6) complete information has been collected. Documentation: should follow construction progress at any time finishing self acceptance, signature acceptance after the representatives of the party were invited. Requirements: (1) covert acceptance is thea the company's situation, familiar with the period schedule master plan, construction with water, power supply, vertical transportation, gondola of external scaffolding or construction. (2) technical data preparation: first drawings to prepare the drawings to be fully familiar with, and does not have difficult places to ask out clearly understood, you also need to prepare acceptance of the Atlas, the quality standards, safety index, all the forms used and the acceptance required for the works, and more. (3) tools, implements preparation: supply planning against the required tools, appliances, specific to the type, quantity, supply time, also plans to supply, warehouse, and other departments, common tools and appliances. (4) materials: according to the drawings and engineering, detailed material supply meter ... (2) preparations into people, and clear accountability to specific persons. (3) implementation of collaboration and cooperation with construction companies. 2.15 embedded part installation (early works with civil engineering completed) 1. Note: buried is one of the curtain wall with main structure connecting structure, embedded quality directly affects the production, installation of curtain wall and the main structure of the connections. Its installation has a direct impact on the degree of precision of curtain wall construction accuracy and surface quality is good or bad. So the first job as a curtain wall installation, buried both for its manufacture and installation are directly affects the entire curtain wall construction, installation, and an important factor in the overall effect. 2. material specifications: the embedded parts. 3. basic operation: (1) familiar with the drawings: installation personnel after receivingtypeset by the owners ' consent before they can purchase and order under the program, each stone must use the same background, the same pattern, size error in 0.5mm stone. Air infiltration properties, stone curtain wall wind pressure rainwater leakage in distortion performance, performance and energy-saving performance in front of the construction should be in accordance with the construction plan of the specification and the file size in the appropriate authority inspection departments qualified testing. Stone used steel keel, installation job main including following steps: 2.1 construction Qian prepared 2.2 pre buried pieces processing 2.3 measurement and the measurement results figure draws 2.4 vertical box positioning put line 2.5 turned received pieces installation 2.6 vertical box installation 2.7 vertical box correction and acceptance 2.8 layer high and the cross box measurement positioning and put line 2.9 cross box installation 2.10 installation 2.11 stone plate installation 2.12 sealed rubber injection 2.13 clean ending 2.14 construction Qian prepared 1. Description Project Manager required for the duration of the project schedule, technical information, tools, machinery, apparatus, materials, personnel, temporary facilities ready. 2. the scope of previous construction (1) project outline: to understand the site profiles, familiar with the construction and supervision of party 精品练习答案: 1.解析:小车静止或匀速直线运动时，小球也处于静止或匀速直线运动状态。由平衡条件可知，绳子对小球的弹力为，方向是沿着绳子向上。 若将轻绳换成轻弹簧，其结果是一样的。 2.解析:以小球为研究对象，可知小球受到杆对它一个的弹力和重力作用，由平衡条件可知小球受力如图所示。则可知杆对小球的弹力为，方向与重力的方向相反即竖直向上。 注意:在这里杆对小球的作用力方向不是沿着杆的方向。 3.解析:以小球为研究对象进行受力分析，如图4所示。根据小球做匀加速直线运动可 得在竖直方向 在水平方向 解之得 轻绳对小球的作用力大小随着加速度的增大而增大，它的方向沿着绳子，与竖直方向的夹角为。 4.解析:如图，小球受到重力和杆对它的弹力F作用而随小车一起向左做匀加速直线运动。 在竖直方向 在水平方向 解之得。 由解答可知，轻杆对小球的作用力大小随着加速度的增大而增大，它的方向不一定沿着杆的方向，而是随着加速度大小的变化而变化。只有时，F才沿着杆的方向。 5.解析:在没有剪断之前对小球进行受力如图所示，由平衡 条件可得，。 当剪断水平细线AB时，此时小球由于细线OB的限制，在 沿OB方向上，小球不可能运动，故小球只能沿着与OB垂直的方向运动，也就是说小球所that construction site clean, consciously maintain sanitation. (4) ensure the safety of materials and semi-finished products. 8. quality assessment, data compilation: buried, belongs to the concealed works construction, therefore its quality inspection must be carried out according to acceptance of concealed work-related. Mainly in the following aspects: (1) acceptance of positioning is accurate. (2) is fixed securely. (3) tightening compliance requirements. (4) have an impact on other projects. (5) the material used is eligible. (6) complete information has been collected. Documentation: should follow construction progress at any time finishing self acceptance, signature acceptance after the representatives of the party were invited. Requirements: (1) covert acceptance is thea the company's situation, familiar with the period schedule master plan, construction with water, power supply, vertical transportation, gondola of external scaffolding or construction. (2) technical data preparation: first drawings to prepare the drawings to be fully familiar with, and does not have difficult places to ask out clearly understood, you also need to prepare acceptance of the Atlas, the quality standards, safety index, all the forms used and the acceptance required for the works, and more. (3) tools, implements preparation: supply planning against the required tools, appliances, specific to the type, quantity, supply time, also plans to supply, warehouse, and other departments, common tools and appliances. (4) materials: according to the drawings and engineering, detailed material supply meter ... (2) preparations into people, and clear accountability to specific persons. (3) implementation of collaboration and cooperation with construction companies. 2.15 embedded part installation (early works with civil engineering completed) 1. Note: buried is one of the curtain wall with main structure connecting structure, embedded quality directly affects the production, installation of curtain wall and the main structure of the connections. Its installation has a direct impact on the degree of precision of curtain wall construction accuracy and surface quality is good or bad. So the first job as a curtain wall installation, buried both for its manufacture and installation are directly affects the entire curtain wall construction, installation, and an important factor in the overall effect. 2. material specifications: the embedded parts. 3. basic operation: (1) familiar with the drawings: installation personnel after receivingtypeset by the owners ' consent before they can purchase and order under the program, each stone must use the same background, the same pattern, size error in 0.5mm stone. Air infiltration properties, stone curtain wall wind pressure rainwater leakage in distortion performance, performance and energy-saving performance in front of the construction should be in accordance with the construction plan of the specification and the file size in the appropriate authority inspection departments qualified testing. Stone used steel keel, installation job main including following steps: 2.1 construction Qian prepared 2.2 pre buried pieces processing 2.3 measurement and the measurement results figure draws 2.4 vertical box positioning put line 2.5 turned received pieces installation 2.6 vertical box installation 2.7 vertical box correction and acceptance 2.8 layer high and the cross box measurement positioning and put line 2.9 cross box installation 2.10 installation 2.11 stone plate installation 2.12 sealed rubber injection 2.13 clean ending 2.14 construction Qian prepared 1. Description Project Manager required for the duration of the project schedule, technical information, tools, machinery, apparatus, materials, personnel, temporary facilities ready. 2. the scope of previous construction (1) project outline: to understand the site profiles, familiar with the construction and supervision of party 受到的重力，此时的作用效果是拉绳和沿垂直绳的方向做加速运动，其受力如图所示。由图可知，则可得方向垂直于OB向下。绳OB的拉力，则可知当剪断水平细线AB时，细线OB的拉力发生了突变。 6.解析:在细线未剪断前，由平衡条件可得 水平细线的拉力 弹簧的拉力 当剪断细线的瞬时，，而弹簧形变不能马上改变，故弹簧弹力F保持原值。在图所示中，。所以在剪断细线的瞬时F和mg的合力仍等于原的大小，方向水平向右。则可知小球的加速度方向沿水平向右，即与竖直成角，其大小为。 that construction site clean, consciously maintain sanitation. (4) ensure the safety of materials and semi-finished products. 8. quality assessment, data compilation: buried, belongs to the concealed works construction, therefore its quality inspection must be carried out according to acceptance of concealed work-related. Mainly in the following aspects: (1) acceptance of positioning is accurate. (2) is fixed securely. (3) tightening compliance requirements. (4) have an impact on other projects. (5) the material used is eligible. (6) complete information has been collected. Documentation: should follow construction progress at any time finishing self acceptance, signature acceptance after the representatives of the party were invited. Requirements: (1) covert acceptance is thea the company's situation, familiar with the period schedule master plan, construction with water, power supply, vertical transportation, gondola of external scaffolding or construction. (2) technical data preparation: first drawings to prepare the drawings to be fully familiar with, and does not have difficult places to ask out clearly understood, you also need to prepare acceptance of the Atlas, the quality standards, safety index, all the forms used and the acceptance required for the works, and more. (3) tools, implements preparation: supply planning against the required tools, appliances, specific to the type, quantity, supply time, also plans to supply, warehouse, and other departments, common tools and appliances. (4) materials: according to the drawings and engineering, detailed material supply meter ... (2) preparations into people, and clear accountability to specific persons. (3) implementation of collaboration and cooperation with construction companies. 2.15 embedded part installation (early works with civil engineering completed) 1. Note: buried is one of the curtain wall with main structure connecting structure, embedded quality directly affects the production, installation of curtain wall and the main structure of the connections. Its installation has a direct impact on the degree of precision of curtain wall construction accuracy and surface quality is good or bad. So the first job as a curtain wall installation, buried both for its manufacture and installation are directly affects the entire curtain wall construction, installation, and an important factor in the overall effect. 2. material specifications: the embedded parts. 3. basic operation: (1) familiar with the drawings: installation personnel after receivingtypeset by the owners ' consent before they can purchase and order under the program, each stone must use the same background, the same pattern, size error in 0.5mm stone. Air infiltration properties, stone curtain wall wind pressure rainwater leakage in distortion performance, performance and energy-saving performance in front of the construction should be in accordance with the construction plan of the specification and the file size in the appropriate authority inspection departments qualified testing. Stone used steel keel, installation job main including following steps: 2.1 construction Qian prepared 2.2 pre buried pieces processing 2.3 measurement and the measurement results figure draws 2.4 vertical box positioning put line 2.5 turned received pieces installation 2.6 vertical box installation 2.7 vertical box correction and acceptance 2.8 layer high and the cross box measurement positioning and put line 2.9 cross box installation 2.10 installation 2.11 stone plate installation 2.12 sealed rubber injection 2.13 clean ending 2.14 construction Qian prepared 1. Description Project Manager required for the duration of the project schedule, technical information, tools, machinery, apparatus, materials, personnel, temporary facilities ready. 2. the scope of previous construction (1) project outline: to understand the site profiles, familiar with the construction and supervision of party