{"id":1187,"date":"2015-08-25T12:05:06","date_gmt":"2015-08-25T12:05:06","guid":{"rendered":"http:\/\/fisicaevestibular.com.br\/novo\/?page_id=1187"},"modified":"2024-08-23T13:43:19","modified_gmt":"2024-08-23T13:43:19","slug":"resolucao-comentada-dos-exercicios-de-vestibulares-sobre-polias-ou-roldanas","status":"publish","type":"page","link":"https:\/\/fisicaevestibular.com.br\/novo\/mecanica\/dinamica\/polias-e-roldanas\/resolucao-comentada-dos-exercicios-de-vestibulares-sobre-polias-ou-roldanas\/","title":{"rendered":"Polias ou Roldanas &#8211; Resolu\u00e7\u00e3o"},"content":{"rendered":"<p align=\"CENTER\"><span style=\"color: #0000cc;\"><span style=\"font-family: 'Arial Black', serif;\"><span style=\"font-size: large;\"><b>Resolu\u00e7\u00e3o comentada dos exerc\u00edcios de vestibulares sobre<\/b><\/span><\/span><\/span><\/p>\n<p align=\"CENTER\"><span style=\"color: #c00000;\"><span style=\"font-family: 'Arial Black', serif;\"><span style=\"font-size: large;\"><b>Polias ou Roldanas<\/b><\/span><\/span><\/span><\/p>\n<p><span style=\"color: #000000;\">\u00a0<\/span><\/p>\n<p><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>01<\/b><\/span><\/span><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>&#8211; Observe que temos duas polias m\u00f3veis\u00a0 &#8212;\u00a0 n=2\u00a0 &#8212;\u00a0 F =25\/2<\/b><\/span><\/span><sup><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>n<\/b><\/span><\/span><\/sup><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>\u00a0 &#8212;\u00a0 25 = Q\/2<\/b><\/span><\/span><sup><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>2<\/b><\/span><\/span><\/sup><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>\u00a0 &#8212;\u00a0\u00a0<\/b><\/span><\/span><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>Q = 100N<\/b><\/span><\/span><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>.<\/b><\/span><\/span><\/p>\n<p><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>02<\/b><\/span><\/span><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>&#8211; a) Uma roldana m\u00f3vel, o homem deve aplicar uma for\u00e7a 2<\/b><\/span><\/span><sup><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>n<\/b><\/span><\/span><\/sup><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>=2<\/b><\/span><\/span><sup><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>1<\/b><\/span><\/span><\/sup><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>=2 vezes menor, ou seja, de 550\/2=275N.<\/b><\/span><\/span><\/p>\n<p><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>b) Duas vezes menor, ou seja, de 0,5m.<\/b><\/span><\/span><\/p>\n<p><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>03<\/b><\/span><\/span><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>&#8211; O dinam\u00f4metro indica a intensidade da for\u00e7a que traciona o fio que est\u00e1 preso ao solo, ou seja, 400N. Observe na figura, que a<\/b><\/span><\/span><\/p>\n<p align=\"CENTER\"><img fetchpriority=\"high\" decoding=\"async\" src=\"http:\/\/fisicaevestibular.com.br\/novo\/wp-content\/uploads\/migracao\/polias\/i_0ab260d6d4034b45_html_196e33c4.jpg\" alt=\"\" width=\"230\" height=\"236\" name=\"graphics14\" align=\"BOTTOM\" border=\"0\" \/><\/p>\n<p><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>distribui\u00e7\u00e3o de for\u00e7as nos fornece o peso do bloco, 50N. Como P=m.g\u00a0 &#8212;\u00a0 50=m.10\u00a0 &#8212;\u00a0\u00a0<\/b><\/span><\/span><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>m=5kg<\/b><\/span><\/span><\/p>\n<p><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>04<\/b><\/span><\/span><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>&#8211; Peso do carro\u00a0 &#8212;\u00a0 P<\/b><\/span><\/span><sub><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>C<\/b><\/span><\/span><\/sub><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>=m.g\u00a0 &#8212;\u00a0 P<\/b><\/span><\/span><sub><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>C<\/b><\/span><\/span><\/sub><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>=700.10\u00a0 &#8212;\u00a0 P<\/b><\/span><\/span><sub><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>C<\/b><\/span><\/span><\/sub><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>=7000N\u00a0<\/b><\/span><\/span><\/p>\n<p><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>Chamando de P o peso do contrapeso, de m sua massa, e colocando todas as for\u00e7as, observamos<\/b><\/span><\/span><\/p>\n<p align=\"CENTER\"><img decoding=\"async\" src=\"http:\/\/fisicaevestibular.com.br\/novo\/wp-content\/uploads\/migracao\/polias\/i_0ab260d6d4034b45_html_65642cdb.jpg\" alt=\"\" width=\"418\" height=\"238\" name=\"Imagem 7\" align=\"BOTTOM\" border=\"0\" \/><\/p>\n<p><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>que sobre o carro agem as for\u00e7as 7P (para cima) o peso do carro P<\/b><\/span><\/span><sub><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>C<\/b><\/span><\/span><\/sub><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>=7000N (para baixo). Como ele est\u00e1 em equil\u00edbrio\u00a0 &#8212;\u00a0 7P=P<\/b><\/span><\/span><sub><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>C<\/b><\/span><\/span><\/sub><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>\u00a0 &#8212;\u00a0 7P=7000\u00a0 &#8212;\u00a0 P=1000N e m=100kg.\u00a0<\/b><\/span><\/span><\/p>\n<p><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>O cabo central exerce uma for\u00e7a de 2P (veja figura)\u00a0 &#8212;\u00a0 F=2.1000\u00a0 &#8212;\u00a0 F=2000N<\/b><\/span><\/span><\/p>\n<p><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>05<\/b><\/span><\/span><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>&#8211; Observe a figura abaixo:<\/b><\/span><\/span><\/p>\n<p align=\"CENTER\"><img decoding=\"async\" src=\"http:\/\/fisicaevestibular.com.br\/novo\/wp-content\/uploads\/migracao\/polias\/i_0ab260d6d4034b45_html_47daf4de.jpg\" alt=\"\" width=\"354\" height=\"272\" name=\"graphics15\" align=\"BOTTOM\" border=\"0\" \/><\/p>\n<p><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>R- A<\/b><\/span><\/span><\/p>\n<p><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>06<\/b><\/span><\/span><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>&#8211; Tr\u00eas polias m\u00f3veis n=3\u00a0 &#8212;\u00a0 2<\/b><\/span><\/span><sup><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>n<\/b><\/span><\/span><\/sup><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>=2<\/b><\/span><\/span><sup><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>3<\/b><\/span><\/span><\/sup><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>=8 vezes menor<\/b><\/span><\/span><\/p>\n<p><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>07<\/b><\/span><\/span><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>&#8211; P=m.g\u00a0 &#8212;\u00a0 P=8.10\u00a0 &#8212;\u00a0 P=80N\u00a0 &#8212;\u00a0 Observe nas figuras abaixo as distribui\u00e7\u00f5es de for\u00e7as.<\/b><\/span><\/span><\/p>\n<p align=\"CENTER\"><img loading=\"lazy\" decoding=\"async\" src=\"http:\/\/fisicaevestibular.com.br\/novo\/wp-content\/uploads\/migracao\/polias\/i_0ab260d6d4034b45_html_e2408494.jpg\" alt=\"\" width=\"192\" height=\"228\" name=\"Imagem 9\" align=\"BOTTOM\" border=\"0\" \/> <img loading=\"lazy\" decoding=\"async\" src=\"http:\/\/fisicaevestibular.com.br\/novo\/wp-content\/uploads\/migracao\/polias\/i_0ab260d6d4034b45_html_a6473ce0.jpg\" alt=\"\" width=\"196\" height=\"228\" name=\"graphics16\" align=\"BOTTOM\" border=\"0\" \/><\/p>\n<p><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>Observe tamb\u00e9m que no esquema A todas as polias s\u00e3o fixas e o peso do bloco \u00e9 transmitido integralmente (F<\/b><\/span><\/span><sub><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>A<\/b><\/span><\/span><\/sub><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>=80N).<\/b><\/span><\/span><\/p>\n<p><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>No esquema B temos uma polia m\u00f3vel e o peso do bloco cai pela metade.<\/b><\/span><\/span><\/p>\n<p><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>08<\/b><\/span><\/span><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>&#8211; For\u00e7as que agem sobre voc\u00ea\u00a0 &#8212;\u00a0 seu peso de intensidade\u00a0 &#8212;\u00a0 P=m.g\u00a0 &#8212;\u00a0 P=60.10\u00a0 &#8212;\u00a0 P=600N\u00a0\u00a0 e a indica\u00e7\u00e3o da balan\u00e7a N<\/b><\/span><\/span><\/p>\n<p align=\"CENTER\"><img loading=\"lazy\" decoding=\"async\" src=\"http:\/\/fisicaevestibular.com.br\/novo\/wp-content\/uploads\/migracao\/polias\/i_0ab260d6d4034b45_html_124ede87.jpg\" alt=\"\" width=\"57\" height=\"121\" name=\"Imagem 11\" align=\"BOTTOM\" border=\"0\" \/><\/p>\n<p><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>Desce acelerando\u00a0 &#8212;\u00a0 P \u2013 N = m.a\u00a0 &#8212;\u00a0 600 \u2013 N=60.3\u00a0 &#8212; \u00a0-N=180 \u2013 600\u00a0 &#8212;\u00a0 N=420N\u00a0 &#8212;\u00a0 voc\u00ea se sente \u201cmais leve\u201d (peso aparente).<\/b><\/span><\/span><\/p>\n<p><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>09<\/b><\/span><\/span><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>&#8211; a) Quem est\u00e1 sobre a balan\u00e7a \u00e9 a pessoa de massa 70kg e sobre ela agem duas for\u00e7as. Seu peso P para baixo, que ela troca com a Terra, de intensidade P=m.g=70.10\u00a0 &#8212;\u00a0 P=700N e a for\u00e7a normal N para cima, que ela troca com a balan\u00e7a.<\/b><\/span><\/span><\/p>\n<p align=\"CENTER\"><img loading=\"lazy\" decoding=\"async\" src=\"http:\/\/fisicaevestibular.com.br\/novo\/wp-content\/uploads\/migracao\/polias\/i_0ab260d6d4034b45_html_9ae0c10.jpg\" alt=\"\" width=\"96\" height=\"149\" name=\"graphics17\" align=\"BOTTOM\" border=\"0\" \/><\/p>\n<p><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>Como ele sobe acelerando, a balan\u00e7a indicar\u00e1 um valor maior que o peso (N&gt;P)\u00a0 &#8212;\u00a0 F<\/b><\/span><\/span><sub><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>R<\/b><\/span><\/span><\/sub><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>=m.a\u00a0 &#8212;\u00a0 N \u2013 P = m.a\u00a0 &#8212;\u00a0 N \u2013 700=70.3<\/b><\/span><\/span><\/p>\n<p><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>&#8212;\u00a0 N=700 + 210\u00a0 &#8212;\u00a0\u00a0<\/b><\/span><\/span><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>N=910N<\/b><\/span><\/span><\/p>\n<p><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>b) A for\u00e7a de tra\u00e7\u00e3o para cima nos cabos est\u00e1 puxando o elevador mais a pessoa (sistema) de peso\u00a0 &#8212;\u00a0 P=(1000 + 70).10\u00a0 &#8212;\u00a0<\/b><\/span><\/span><\/p>\n<p><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>P=10.700N.<\/b><\/span><\/span><\/p>\n<p align=\"CENTER\"><img loading=\"lazy\" decoding=\"async\" src=\"http:\/\/fisicaevestibular.com.br\/novo\/wp-content\/uploads\/migracao\/polias\/i_0ab260d6d4034b45_html_5a912833.jpg\" alt=\"\" width=\"113\" height=\"222\" name=\"Imagem 13\" align=\"BOTTOM\" border=\"0\" \/><\/p>\n<p>\u00a0<span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>Como ele sobe acelerando T&gt;P\u00a0 &#8212;\u00a0 F<\/b><\/span><\/span><sub><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>R<\/b><\/span><\/span><\/sub><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>m.a\u00a0 &#8212;\u00a0 T \u2013 10.700 = 1.070.3\u00a0 &#8212;T=10.700 + 3.210\u00a0 &#8212;\u00a0 T= 13.910N<\/b><\/span><\/span><\/p>\n<p><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>Como temos tr\u00eas cabos, a for\u00e7a de tra\u00e7\u00e3o em cada cabo ser\u00e1 13.910\/3\u00a0 &#8212;\u00a0\u00a0<\/b><\/span><\/span><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>T=4.636,7N<\/b><\/span><\/span><\/p>\n<p><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>c) A pessoa bateria com a cabe\u00e7a no teto e depois cairia com a mesma acelera\u00e7\u00e3o e velocidades que o elevador.<\/b><\/span><\/span><\/p>\n<p><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>10<\/b><\/span><\/span><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>&#8211; O peso aparente corresponde \u00e0 for\u00e7a normal N\u00a0 &#8212;\u00a0\u00a0 F<\/b><\/span><\/span><sub><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>R<\/b><\/span><\/span><\/sub><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>=ma\u00a0 &#8212;\u00a0 P \u2013 N=m.a\u00a0 &#8212;\u00a0 100 \u2013 N =10.5\u00a0 &#8212;\u00a0 N=50N.<\/b><\/span><\/span><\/p>\n<p><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>11<\/b><\/span><\/span><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>&#8211; Sobre o corpo agem duas for\u00e7as. A indica\u00e7\u00e3o do dinam\u00f4metro para cima (T=2,5N) e o peso para baixo (P=2,0N). Sendo T&gt;P, ele est\u00e1 subindo e acelerando ou descendo e freando. R- D<\/b><\/span><\/span><\/p>\n<p><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>12<\/b><\/span><\/span><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>&#8211; A tra\u00e7\u00e3o m\u00e1xima suportada pelo cabo vale T=m.g=1200.10\u00a0 &#8212;\u00a0 T=12.000N.<\/b><\/span><\/span><\/p>\n<p align=\"CENTER\"><img loading=\"lazy\" decoding=\"async\" src=\"http:\/\/fisicaevestibular.com.br\/novo\/wp-content\/uploads\/migracao\/polias\/i_0ab260d6d4034b45_html_840ba82c.jpg\" alt=\"\" width=\"128\" height=\"183\" name=\"Imagem 14\" align=\"BOTTOM\" border=\"0\" \/><\/p>\n<p><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>O peso do elevador \u00e9 de P=1000.10\u00a0 &#8212;\u00a0 P=10.000N.\u00a0 &#8212;\u00a0 sobe acelerando &#8211; T&gt;P\u00a0 &#8212;\u00a0 F<\/b><\/span><\/span><sub><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>R<\/b><\/span><\/span><\/sub><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>=m.a\u00a0 &#8212;\u00a0 T \u2013 P =m.a\u00a0 &#8212;\u00a0 12000 \u2013 10.000=<\/b><\/span><\/span><\/p>\n<p><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>1.000.a\u00a0 &#8212;\u00a0\u00a0<\/b><\/span><\/span><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>a=2m\/s<\/b><\/span><\/span><sup><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>2<\/b><\/span><\/span><\/sup><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>.<\/b><\/span><\/span><\/p>\n<p><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>13<\/b><\/span><\/span><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>&#8211; O peso da pessoa \u00e9 constante e vale\u00a0 &#8212;\u00a0 P=m.g\u00a0 &#8212;\u00a0 P=80g (g \u00e9 pedido)\u00a0 &#8212;\u00a0 Quando o elevador sobe com acelera\u00e7\u00e3o a, N=960N e<\/b><\/span><\/span><\/p>\n<p><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>F<\/b><\/span><\/span><sub><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>R<\/b><\/span><\/span><\/sub><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>=ma\u00a0 &#8212;\u00a0 N \u2013 P=ma\u00a0 &#8212;<\/b><\/span><\/span><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>\u00a0960 \u2013 80g = 80a\u00a0 I<\/b><\/span><\/span><\/p>\n<p><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>Quando o elevador desce com acelera\u00e7\u00e3o a, N=640N e F<\/b><\/span><\/span><sub><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>R<\/b><\/span><\/span><\/sub><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>=ma\u00a0 &#8212;\u00a0 P \u2013 N=ma\u00a0 &#8212;\u00a0\u00a0<\/b><\/span><\/span><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>80g \u2013 640=80a<\/b><\/span><\/span><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>\u00a0\u00a0<\/b><\/span><\/span><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>II<\/b><\/span><\/span><\/p>\n<p><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>Somando I com II obtemos\u00a0<\/b><\/span><\/span><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>a=2m\/s<\/b><\/span><\/span><sup><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>2<\/b><\/span><\/span><\/sup><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>, que, substitu\u00eddo em I ou em II nos fornece<\/b><\/span><\/span><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>g=10m\/s<\/b><\/span><\/span><sup><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>2<\/b><\/span><\/span><\/sup><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>.<\/b><\/span><\/span><\/p>\n<p><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>Ent\u00e3o o peso da pessoa \u00e9 P=mg\u00a0 &#8212;\u00a0 P=80.10\u00a0 &#8212;\u00a0 P=800N. Quando a balan\u00e7a registrar 800N est\u00e1 registrando o peso da pessoa e nesse caso o elevador estar\u00e1 em repouso ou subindo ou descendo em MRU.<\/b><\/span><\/span><\/p>\n<p><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>Quando a balan\u00e7a registrar zero o elevador e a pessoa est\u00e3o em queda livre.<\/b><\/span><\/span><\/p>\n<p><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>14<\/b><\/span><\/span><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>&#8211; Os \u00f3rg\u00e3os internos s\u00f3 se movem ou tendem a se mover, por in\u00e9rcia, quando houver varia\u00e7\u00e3o de velocidade, ou seja, surgir acelera\u00e7\u00e3o. R- D<\/b><\/span><\/span><\/p>\n<p><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>15<\/b><\/span><\/span><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>&#8211; Se indica um peso maior, N&gt;P e o elevador pode estar subindo e acelerando ou descendo e freando. R- C<\/b><\/span><\/span><\/p>\n<p><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>16<\/b><\/span><\/span><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>&#8211; P=m.g\u00a0 &#8212;\u00a0 P=0,8.10\u00a0 &#8212;\u00a0 P=8,0N\u00a0 &#8212;\u00a0 tra\u00e7\u00e3o m\u00e1xima que o fio suporta\u00a0 &#8212;\u00a0 T=9,6N\u00a0 &#8212;\u00a0 F<\/b><\/span><\/span><sub><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>R<\/b><\/span><\/span><\/sub><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>=m.a\u00a0 &#8212;\u00a0 T \u2013 P=ma\u00a0 &#8212;\u00a0 9,6 \u2013 8,0=0,8.a\u00a0 &#8212;\u00a0 a=1,6\/0,8\u00a0 &#8212;\u00a0 a=2,0m\/s<\/b><\/span><\/span><sup><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>2<\/b><\/span><\/span><\/sup><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>. Como T&gt;P, ele sobe acelerando ou desce freando. R- C<\/b><\/span><\/span><\/p>\n<p><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>17<\/b><\/span><\/span><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>&#8211; Vamos colocar todas as for\u00e7as que agem sobre o homem e sobre o elevador<\/b><\/span><\/span><\/p>\n<p align=\"CENTER\"><img loading=\"lazy\" decoding=\"async\" src=\"http:\/\/fisicaevestibular.com.br\/novo\/wp-content\/uploads\/migracao\/polias\/i_0ab260d6d4034b45_html_e4b3bac8.jpg\" alt=\"\" width=\"213\" height=\"327\" name=\"Imagem 15\" align=\"BOTTOM\" border=\"0\" \/><\/p>\n<p><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>P<\/b><\/span><\/span><sub><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>e<\/b><\/span><\/span><\/sub><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>\u00a0\u2013 peso do elevador\u00a0 &#8212;\u00a0 P<\/b><\/span><\/span><sub><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>e<\/b><\/span><\/span><\/sub><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>=Mg\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 P<\/b><\/span><\/span><sub><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>H<\/b><\/span><\/span><\/sub><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>\u00a0\u2013 peso do homem\u00a0 &#8212;\u00a0 P<\/b><\/span><\/span><sub><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>H<\/b><\/span><\/span><\/sub><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>=mg\u00a0 &#8212;\u00a0 N \u2013 for\u00e7a trocada entre o homem e o piso do elevador\u00a0 &#8212;\u00a0 T \u2013 for\u00e7a de tra\u00e7\u00e3o na corda que puxa o homem e o elevador para cima.<\/b><\/span><\/span><\/p>\n<p><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>Homem\u00a0 &#8212;\u00a0 F<\/b><\/span><\/span><sub><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>R<\/b><\/span><\/span><\/sub><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>=ma\u00a0 &#8212;\u00a0 T + N &#8211; P<\/b><\/span><\/span><sub><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>H<\/b><\/span><\/span><\/sub><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>=ma\u00a0 &#8212;\u00a0\u00a0<\/b><\/span><\/span><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>T + N \u2013 mg = ma\u00a0 I<\/b><\/span><\/span><\/p>\n<p><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>Elevador\u00a0 &#8212;\u00a0 F<\/b><\/span><\/span><sub><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>R<\/b><\/span><\/span><\/sub><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>=Ma\u00a0 &#8212;\u00a0 T \u2013 P<\/b><\/span><\/span><sub><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>e<\/b><\/span><\/span><\/sub><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>\u00a0\u2013 N = Ma\u00a0 &#8212;\u00a0\u00a0<\/b><\/span><\/span><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>T \u2013 Mg \u2013 N = Ma\u00a0 II<\/b><\/span><\/span><\/p>\n<p><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>Somando I com II\u00a0 &#8212;\u00a0 2T \u2013 Mg \u2013 mg = Ma + ma\u00a0 &#8212;\u00a0 2T = (M + m)g + (M + m)a\u00a0 &#8212;\u00a0\u00a0<\/b><\/span><\/span><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>T=(M + m).(a + g)\/2<\/b><\/span><\/span><\/p>\n<p><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>18<\/b><\/span><\/span><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>&#8211; a=g\/5\u00a0 &#8212;\u00a0 Desce acelerando\u00a0 &#8212;\u00a0 N&lt;P\u00a0 &#8212;\u00a0 F<\/b><\/span><\/span><sub><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>R<\/b><\/span><\/span><\/sub><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>=m.a\u00a0 &#8212;\u00a0 P \u2013 N=m.a\u00a0 &#8212;\u00a0\u00a0\u00a0 m.g \u2013 N=m.g\/5\u00a0 &#8212;\u00a0 N=(5mg \u2013 mg)\/5\u00a0 &#8212;\u00a0\u00a0<\/b><\/span><\/span><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>N=4mg\/5\u00a0 I<\/b><\/span><\/span><\/p>\n<p><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>P=mg\u00a0 II\u00a0\u00a0<\/b><\/span><\/span><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>&#8212;\u00a0 Dividindo I por II\u00a0 &#8212;\u00a0 N\/P=4mg\/5X1\/mg\u00a0 &#8212;\u00a0\u00a0<\/b><\/span><\/span><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>N\/P=4\/5\u00a0\u00a0<\/b><\/span><\/span><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>R- D<\/b><\/span><\/span><\/p>\n<p><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>19<\/b><\/span><\/span><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>&#8211; Sobre o elevador temos T=4f=4.1350\u00a0 &#8212;\u00a0 T=5400N (para cima) e P=mg=600.10\u00a0\u00a0 &#8212;\u00a0 P=6000N (para baixo).\u00a0 &#8212;\u00a0 F<\/b><\/span><\/span><sub><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>R<\/b><\/span><\/span><\/sub><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>=ma\u00a0 &#8212;\u00a0<\/b><\/span><\/span><\/p>\n<p><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>P \u2013 T=m.a\u00a0 &#8212;\u00a0 6000 \u2013 5400=600.a\u00a0 &#8212;\u00a0 a=600\/600\u00a0 &#8212;\u00a0\u00a0<\/b><\/span><\/span><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>a=1m\/s<\/b><\/span><\/span><sup><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>2<\/b><\/span><\/span><\/sup><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>.<\/b><\/span><\/span><\/p>\n<p><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>20<\/b><\/span><\/span><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>&#8211; Considerando o sistema, elevador mais pessoa de massas (M + m)\u00a0 &#8212;\u00a0 desce freando\u00a0 &#8212;\u00a0 T&gt;P\u00a0 &#8212;\u00a0 F<\/b><\/span><\/span><sub><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>R<\/b><\/span><\/span><\/sub><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>=m.a\u00a0 &#8212;\u00a0 T \u2013 P=(M + m).a\u00a0\u00a0 &#8212;\u00a0 T \u2013 (M + m).g= (M + m).a\u00a0 &#8212;\u00a0\u00a0<\/b><\/span><\/span><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>T=(M + m).(a + g)\u00a0 R- B<\/b><\/span><\/span><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>\u00a0\u00a0\u00a0\u00a0\u00a0<\/b><\/span><\/span><\/p>\n<p><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>21<\/b><\/span><\/span><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>&#8211; Colocando a for\u00e7a pedida e o peso que interessa:<\/b><\/span><\/span><\/p>\n<p align=\"CENTER\"><img loading=\"lazy\" decoding=\"async\" src=\"http:\/\/fisicaevestibular.com.br\/novo\/wp-content\/uploads\/migracao\/polias\/i_0ab260d6d4034b45_html_9b2c846c.jpg\" alt=\"\" width=\"501\" height=\"203\" name=\"Imagem 16\" align=\"BOTTOM\" border=\"0\" \/><\/p>\n<p><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>Como o bloco de massa 2m sobe freando com acelera\u00e7\u00e3o a, N&lt;P\u00a0 &#8212;\u00a0 F<\/b><\/span><\/span><sub><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>R<\/b><\/span><\/span><\/sub><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>\u00a0=m.a\u00a0 &#8212;\u00a0 P \u2013 N=2m.a\u00a0 &#8212;\u00a0 2mg \u2013 N=2m.a\u00a0 &#8212;\u00a0<\/b><\/span><\/span><\/p>\n<p><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>N=2m(g \u2013 a).<\/b><\/span><\/span><\/p>\n<p><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>22-<\/b><\/span><\/span><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>O astronauta tem que descer com acelera\u00e7\u00e3o igual \u00e0 da gravidade da Lua que \u00e9 20% da terrestre\u00a0<\/b><\/span><\/span><\/p>\n<p align=\"CENTER\"><img loading=\"lazy\" decoding=\"async\" src=\"http:\/\/fisicaevestibular.com.br\/novo\/wp-content\/uploads\/migracao\/polias\/i_0ab260d6d4034b45_html_74d34968.jpg\" alt=\"\" width=\"437\" height=\"196\" name=\"graphics18\" align=\"BOTTOM\" border=\"0\" \/><\/p>\n<p><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>&#8212;\u00a0 a<\/b><\/span><\/span><sub><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>l<\/b><\/span><\/span><\/sub><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>=0,2.10=2m\/s<\/b><\/span><\/span><sup><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>2<\/b><\/span><\/span><\/sup><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>\u00a0 &#8212; \u00a0\u00a0observe a figura 1 onde est\u00e3o colocadas as for\u00e7as que agem sobre o astronauta &#8212;\u00a0 F<\/b><\/span><\/span><sub><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>R<\/b><\/span><\/span><\/sub><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>=m.a\u00a0 &#8212;\u00a0 P<\/b><\/span><\/span><sub><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>a<\/b><\/span><\/span><\/sub><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>\u00a0\u2013 T = m<\/b><\/span><\/span><sub><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>a<\/b><\/span><\/span><\/sub><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>.a<\/b><\/span><\/span><sub><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>L<\/b><\/span><\/span><\/sub><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>\u00a0 &#8212;\u00a0 220.10 &#8211; T = 220.2\u00a0 &#8212;<\/b><\/span><\/span><\/p>\n<p><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>T=2200 \u2013 440\u00a0 &#8212;\u00a0 T= 1760N\u00a0 &#8212;\u00a0 essa tra\u00e7\u00e3o \u00e9 transmitida at\u00e9 o contrapeso\u00a0 &#8212;\u00a0 figura 2\u00a0 &#8212;\u00a0 o contrapeso deve subir com a mesma acelera\u00e7\u00e3o que o astronauta est\u00e1 descendo, ou seja, a<\/b><\/span><\/span><sub><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>L<\/b><\/span><\/span><\/sub><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>=2m\/s<\/b><\/span><\/span><sup><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>2<\/b><\/span><\/span><\/sup><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>\u00a0 &#8212;\u00a0 F<\/b><\/span><\/span><sub><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>R<\/b><\/span><\/span><\/sub><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>=m<\/b><\/span><\/span><sub><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>c<\/b><\/span><\/span><\/sub><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>.a<\/b><\/span><\/span><sub><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>L<\/b><\/span><\/span><\/sub><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>\u00a0 &#8212;\u00a0 2T \u2013\u00a0 P<\/b><\/span><\/span><sub><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>c<\/b><\/span><\/span><\/sub><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>\u00a0= m<\/b><\/span><\/span><sub><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>c<\/b><\/span><\/span><\/sub><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>.a<\/b><\/span><\/span><sub><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>L<\/b><\/span><\/span><\/sub><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>\u00a0 &#8212;\u00a0 2.1760 = m<\/b><\/span><\/span><sub><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>c<\/b><\/span><\/span><\/sub><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>.10 =<\/b><\/span><\/span><\/p>\n<p><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>M<\/b><\/span><\/span><sub><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>c<\/b><\/span><\/span><\/sub><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>.2\u00a0 &#8212;\u00a0 m<\/b><\/span><\/span><sub><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>c<\/b><\/span><\/span><\/sub><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>\u2248293kg\u00a0 &#8212;\u00a0 como, segundo o enunciado existem for\u00e7as de atrito, este resultado \u00e9 aproximado eest\u00e1 mais pr\u00f3xima da alternativa A\u00a0 &#8212;\u00a0\u00a0<\/b><\/span><\/span><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>R- A<\/b><\/span><\/span><\/p>\n<p><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>23-<\/b><\/span><\/span><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>Para que a dist\u00e2ncia vertical entre os centros de massa de cada um passe de 9m para 4,5m, o contrapeso deve estar verticalmente mais abaixo que o astronauta e cada um deles deve se deslocar de S=4,5\/2=2,25m (veja figura)\u00a0 &#8212;\u00a0 escolhendo um<\/b><\/span><\/span><\/p>\n<p align=\"CENTER\"><img loading=\"lazy\" decoding=\"async\" src=\"http:\/\/fisicaevestibular.com.br\/novo\/wp-content\/uploads\/migracao\/polias\/i_0ab260d6d4034b45_html_b7bb6f2d.jpg\" alt=\"\" width=\"519\" height=\"218\" name=\"Imagem 18\" align=\"BOTTOM\" border=\"0\" \/><\/p>\n<p><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>deles, por exemplo, o astronauta\u00a0 &#8212;\u00a0 ele deve subir S<\/b><\/span><\/span><sub><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>a<\/b><\/span><\/span><\/sub><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>=2,25m enquanto que no mesmo tempo o contrapeso desce de 2,25m\u00a0 &#8212; \u00a0equa\u00e7\u00e3o do astronauta\u00a0 &#8212;\u00a0 S<\/b><\/span><\/span><sub><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>a<\/b><\/span><\/span><\/sub><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>=S<\/b><\/span><\/span><sub><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>o<\/b><\/span><\/span><\/sub><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>\u00a0+ V<\/b><\/span><\/span><sub><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>o<\/b><\/span><\/span><\/sub><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>t + a.t<\/b><\/span><\/span><sup><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>2<\/b><\/span><\/span><\/sup><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>\/2\u00a0 &#8212;\u00a0 2,25 = 0 + 0.t + 2.t<\/b><\/span><\/span><sup><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>2<\/b><\/span><\/span><\/sup><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>\/2<\/b><\/span><\/span><sup><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>\u00a0<\/b><\/span><\/span><\/sup><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>\u00a0&#8212;\u00a0 t<\/b><\/span><\/span><sup><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>2<\/b><\/span><\/span><\/sup><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>=2,25\u00a0 &#8212;\u00a0 t=1,5s\u00a0 &#8212;\u00a0<\/b><\/span><\/span><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>\u00a0R- D<\/b><\/span><\/span><\/p>\n<p><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>24<\/b><\/span><\/span><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>&#8211;<\/b><\/span><\/span><span style=\"font-family: Arial, serif;\"><span style=\"font-size: medium;\"><b>Pelo enunciado eles se movem com acelera\u00e7\u00f5es de 0,2gTerra, mas como existe atrito essa acelera\u00e7\u00e3o vai diminuir com a dissipa\u00e7\u00e3o de energia\u00a0 &#8212;\u00a0\u00a0R- B<\/b><\/span><\/span><\/p>\n<p>&nbsp;<\/p>\n<h3><span style=\"color: #000080;\"><a style=\"color: #000080;\" title=\"Exerc\u00edcios de vestibulares com resolu\u00e7\u00f5es comentadas sobre Polias e Roldanas\" href=\"http:\/\/fisicaevestibular.com.br\/novo\/mecanica\/dinamica\/polias-e-roldanas\/exercicios-de-vestibulares-com-resolucoes-comentadas-sobre-polias-e-roldanas\/\">Voltar para os Exerc\u00edcios<\/a><\/span><\/h3>\n","protected":false},"excerpt":{"rendered":"<p>Resolu\u00e7\u00e3o comentada dos exerc\u00edcios de vestibulares sobre Polias ou Roldanas \u00a0 01&#8211; Observe que temos duas polias m\u00f3veis\u00a0 &#8212;\u00a0 n=2\u00a0 &#8212;\u00a0 F =25\/2n\u00a0 &#8212;\u00a0 25 = Q\/22\u00a0 &#8212;\u00a0\u00a0Q = 100N. 02&#8211; a) Uma roldana m\u00f3vel, o homem deve aplicar uma for\u00e7a 2n=21=2 vezes menor, ou seja, de 550\/2=275N. b) Duas vezes menor, ou seja, de 0,5m. 03&#8211; O dinam\u00f4metro indica<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":1183,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"om_disable_all_campaigns":false,"_monsterinsights_skip_tracking":false,"_monsterinsights_sitenote_active":false,"_monsterinsights_sitenote_note":"","_monsterinsights_sitenote_category":0,"footnotes":""},"class_list":["post-1187","page","type-page","status-publish","hentry"],"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/pages\/1187","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/comments?post=1187"}],"version-history":[{"count":3,"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/pages\/1187\/revisions"}],"predecessor-version":[{"id":10853,"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/pages\/1187\/revisions\/10853"}],"up":[{"embeddable":true,"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/pages\/1183"}],"wp:attachment":[{"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/media?parent=1187"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}