Tổng hợp và phân tích lực. Cân bằng lực

Home Lớp 10 Vật lý 10 - Sách kết nối tri thức Bài 13: Tổng hợp và phân tích lực. Cân bằng lựcBài tập nâng cao

{"common":{"save":0,"post_id":"6160","level":3,"total":10,"point":10,"point_extra":0},"segment":[{"id":"5251","mon_id":"1158790","chapter_id":"1158796","post_id":"6160","question":"Có 3 l\u1ef1c \u0111\u1ed3ng quy $\\overrightarrow F_{1}$<\/span> ; $\\overrightarrow F_{2}$<\/span> ; $\\overrightarrow F_{3}$<\/span> nh\u01b0 sau. Nh\u1eadn \u0111\u1ecbnh nào sau \u0111ây là không \u0111úng<\/strong>? <\/p><svg height=\"190\" width=\"179\" xmlns:xlink=\"http:\/\/www.w3.org\/1999\/xlink\"> <g><title><\/title><rect fill=\"#fff\" height=\"192\" id=\"canvas_background\" width=\"181\" x=\"-1\" y=\"-1\"><\/rect> <g display=\"none\" height=\"100%\" id=\"canvasGrid\" overflow=\"visible\" width=\"100%\" x=\"0\" y=\"0\"> <rect fill=\"url(#gridpattern)\" height=\"100%\" stroke-width=\"0\" width=\"100%\" x=\"0\" y=\"0\"><\/rect> <\/g> <\/g> <g><title><\/title><image height=\"218\" id=\"svg_1\" stroke=\"null\" width=\"180.00001\" x=\"1.5\" xlink:href=\"data:image\/png;base64,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\" y=\"-17\"><\/image> <\/g> <\/svg><\/span><\/p>","options":["A. $F_{12}=F_{1}+F_{2}$<\/span>","B. $\\frac{F_{1}}{sin\\beta}=\\frac{F_{2}}{sin\\alpha}$<\/span>","C. $ \\overrightarrow F_{3} \\uparrow\\downarrow \\overrightarrow F_{12}$<\/span>","D. $(\\overrightarrow{F_{1}};\\overrightarrow{F_{2}})=\\alpha +\\beta$<\/span>"],"correct":"1","level":"3","hint":"D\u1ef1a vào hình v\u1ebd, s\u1eed d\u1ee5ng ph\u01b0\u01a1ng pháp t\u1ed5ng h\u1ee3p l\u1ef1c và \u0111\u1ecbnh lí sin \u0111\u1ec3 tr\u1ea3 l\u1eddi câu h\u1ecfi.<\/p><svg height=\"198\" width=\"346\" xmlns:xlink=\"http:\/\/www.w3.org\/1999\/xlink\"> <g><title><\/title><rect fill=\"#fff\" height=\"200\" id=\"canvas_background\" width=\"348\" x=\"-1\" y=\"-1\"><\/rect> <g display=\"none\" height=\"100%\" id=\"canvasGrid\" overflow=\"visible\" width=\"100%\" x=\"0\" y=\"0\"> <rect fill=\"url(#gridpattern)\" height=\"100%\" stroke-width=\"0\" width=\"100%\" x=\"0\" y=\"0\"><\/rect> <\/g> <\/g> <g><title><\/title><image height=\"204\" id=\"svg_1\" width=\"348\" x=\"1.00002\" xlink:href=\"data:image\/png;base64,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\" y=\"0.99999\"><\/image> <\/g> <\/svg><\/span> N\u1ed9i dung \u0111\u1ecbnh lí sin: <\/p>$\\frac{a}{sin\\widehat{A}}=\\frac{b}{sin\\widehat{B}}=\\frac{c}{sin\\widehat{C}}$<\/span><\/p>","answer":"Ch\u1ecdn A<\/strong><\/span>. $\\overrightarrow F_{1}+\\overrightarrow{F_{2} }=\\overrightarrow{F_{12}}\\Rightarrow F_{1}+F_{2}=F_{12}$<\/span>  khi và ch\u1ec9 khi  $(\\overrightarrow{F_{1}};\\overrightarrow{F_{2}})=0$<\/span> °.  Mà α + β ≠ 0° → A sai.<\/p>","type":"choose","extra_type":"classic","user_id":"147","test":"0","date":"2022-08-30 10:20:48","option_type":"math","len":0},{"id":"5252","mon_id":"1158790","chapter_id":"1158796","post_id":"6160","question":"Hai l\u1ef1c $\\overrightarrow F_{1}$<\/span>  và $\\overrightarrow F_{2}$<\/span> có \u0111\u1ed9 l\u1edbn $F_{1}=F_{2}$<\/span> h\u1ee3p v\u1edbi nhau m\u1ed9t góc α. H\u1ee3p l\u1ef1c F c\u1ee7a chúng có \u0111\u1ed9 l\u1edbn<\/p>","options":["A.<\/strong> $F=F_{1}+F_{2}$<\/span>","B.<\/strong> $F=F_{1}-F_{2}$<\/span> ","C. <\/strong> $F = 2F_{1}cos\u03b1$<\/span>","D.<\/strong> $F = 2F_{1}cos\\frac{\u03b1}{2}$<\/span>"],"correct":"4","level":"3","hint":"S\u1eed d\u1ee5ng công th\u1ee9c: $F=\\sqrt{F_{1}^2+F_{2}^2 + 2F_{1}F_{2}cos\\alpha}$<\/span>  và công th\u1ee9c l\u01b0\u1ee3ng giác  $cos^2 x=\\frac{1+cos2x}{2}$<\/span><\/p>","answer":"Ch\u1ecdn D.<\/strong><\/span><\/p><\/span>  $ F^2={F_{1}^2+F_{2}^2 + 2F_{1}F_{2}cos\\alpha} =2F_{1}^2(1+cos\\alpha)=4F_{1}^2\\frac{1+cos\\alpha}{2}=4F_{1}^2cos^2\\frac{\\alpha}{2}$<\/span><\/p>$\\Rightarrow F = 2F_{1}cos\\frac{\u03b1}{2}$<\/span><\/p>","type":"choose","extra_type":"classic","user_id":"147","test":"0","date":"2022-08-30 10:34:22","option_type":"math","len":0},{"id":"5253","mon_id":"1158790","chapter_id":"1158796","post_id":"6160","question":"Ta có l\u1ef1c t\u1ed5ng h\u1ee3p $\\overrightarrow{F}=\\overrightarrow{F_{1}}+\\overrightarrow{F_{2}}$<\/span>  và \u0111\u1ed9 l\u1edbn c\u1ee7a hai l\u1ef1c thành ph\u1ea7n ${F_{1}}=F_{2}=50\\sqrt3N$<\/span> và góc gi\u1eefa l\u1ef1c t\u1ed5ng h\u1ee3p $\\overrightarrow{F}$<\/span>  và  $\\overrightarrow{F_{1}}$<\/span> b\u1eb1ng $\\beta=30$<\/span>° . \u0110\u1ed9 l\u1edbn c\u1ee7a h\u1ee3p l\u1ef1c  $\\overrightarrow{F}$<\/span> và góc gi\u1eefa $\\overrightarrow{F_{1}}$<\/span>  v\u1edbi $\\overrightarrow{F_{2}}$<\/span>  b\u1eb1ng bao nhiêu? <\/p><svg height=\"120\" width=\"195\" xmlns:xlink=\"http:\/\/www.w3.org\/1999\/xlink\"> <g><title><\/title><rect fill=\"#fff\" height=\"122\" id=\"canvas_background\" width=\"197\" x=\"-1\" y=\"-1\"><\/rect> <g display=\"none\" height=\"100%\" id=\"canvasGrid\" overflow=\"visible\" width=\"100%\" x=\"0\" y=\"0\"> <rect fill=\"url(#gridpattern)\" height=\"100%\" stroke-width=\"0\" width=\"100%\" x=\"0\" y=\"0\"><\/rect> <\/g> <\/g> <g><title><\/title><image height=\"157.00001\" id=\"svg_1\" stroke=\"null\" width=\"221.99999\" x=\"-23.5\" xlink:href=\"data:image\/png;base64,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\" y=\"-17.5\"><\/image> <\/g> <\/svg><\/span><\/p>","options":["A. <\/strong>40°;40N","B.<\/strong> 60°; 150N","C.<\/strong> 30°;10N","D.<\/strong> 70°;0N"],"correct":"2","level":"3","hint":"Vì ${F_{1}}=F_{2}$<\/span> mà  $\\overrightarrow{F_{1}}$<\/span>;$\\overrightarrow{F_{2}}$<\/span> t\u1ea1o thành hình bình hành v\u1edbi \u0111\u01b0\u1eddng chéo là $\\overrightarrow{F_{}}$<\/span>  nên α = 2β S\u1eed d\u1ee5ng công th\u1ee9c: $F=\\sqrt{F_{1}^2+F_{2}^2 + 2F_{1}F_{2}cos\\alpha}$<\/span>  tính \u0111\u01b0\u1ee3c F.<\/p>","answer":"Ch\u1ecdn B.<\/strong><\/span> Vì ${F_{1}}=F_{2}$<\/span> mà $\\overrightarrow{F_{1}}$<\/span>;$\\overrightarrow{F_{2}}$<\/span>   t\u1ea1o thành hình bình hành v\u1edbi \u0111\u01b0\u1eddng chéo là $\\overrightarrow{F_{}}$<\/span>  nên  $\u03b1 = 2\u03b2=2.30=60$<\/span>°<\/p>Ta có: $ F^2= F_{1}^2 + F_{2}^2 + 2F_{1}F_{2}.cos\u03b1 = (50\\sqrt3)^2 + (50\\sqrt3)^2 + 2.50\\sqrt3.50\\sqrt3cos60\\circ = 150N$<\/span><\/p>","type":"choose","extra_type":"classic","user_id":"147","test":"0","date":"2022-08-30 10:52:42","option_type":"txt","len":2}]}