{"id":5613,"date":"2020-11-09T03:24:45","date_gmt":"2020-11-09T03:24:45","guid":{"rendered":"http:\/\/fisicaevestibular.com.br\/novo\/?page_id=5613"},"modified":"2024-06-26T14:01:14","modified_gmt":"2024-06-26T14:01:14","slug":"enem-2020-cinematica","status":"publish","type":"page","link":"https:\/\/fisicaevestibular.com.br\/novo\/enem\/enem-2020-cinematica\/","title":{"rendered":"ENEM – 2020 – CINEMATICA"},"content":{"rendered":"

MEC\u00c2NICA<\/span><\/span><\/span><\/p>\n

<\/a>Cinem\u00e1tica<\/span><\/span><\/span><\/p>\n

Movimento Uniforme (MU)<\/span><\/span><\/span><\/p>\n

01-<\/b><\/span><\/span><\/span> <\/b>(ENEM-MEC-019)<\/b><\/span><\/span><\/span><\/span><\/span><\/h4>\n

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A agricultura de precis\u00e3o re\u00fane t\u00e9cnicas agr\u00edcolas que consideram particularidades locais do solo ou lavoura a fim de otimizar o uso de recursos.<\/b><\/span><\/span><\/span><\/span><\/p>\n

Uma das formas de adquirir informa\u00e7\u00f5es sobre essas particularidades\u00a0<\/b><\/span><\/span>\u00e9 a\u00a0<\/b><\/span><\/span>fotografia a\u00e9rea de baixa altitude realizada por um ve\u00edculo a\u00e9reo n\u00e3o tripulado\u00a0<\/b><\/span><\/span>(vant).<\/b><\/span><\/span><\/span><\/span><\/p>\n

Na\u00a0<\/b><\/span><\/span>fase de aquisi\u00e7\u00e3o \u00e9 importante determinar o n\u00edvel de sobreposi\u00e7\u00e3o entre as fotografias.<\/b><\/span><\/span><\/span><\/span><\/p>\n

A figura ilustra como uma sequ\u00eancia de imagens \u00e9 coletada por um vant e como s\u00e3o formadas as sobreposi\u00e7\u00f5es frontais.<\/b><\/span><\/span><\/span><\/span><\/p>\n

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O\u00a0<\/b><\/span><\/span>operador do vant recebe uma encomenda na qual as imagens devem ter uma sobreposi\u00e7\u00e3o frontal de 20% em um terreno plano.\u00a0<\/b><\/span><\/span>Para\u00a0<\/b><\/span><\/span>realizar a aquisi\u00e7\u00e3o das imagens, seleciona uma altitude H fixa de voo de 1 000 m, a uma velocidade constante de 50 m\/s.<\/b><\/span><\/span><\/span><\/span><\/p>\n

A\u00a0<\/b><\/span><\/span>abertura da c\u00e2mera fotogr\u00e1fica do vant \u00e9 de 90\u00b0. Considere tg(45\u00b0) = 1.<\/b><\/span><\/span><\/span><\/span><\/p>\n

Com que intervalo de tempo o operador deve adquirir duas imagens consecutivas?<\/b><\/span><\/span><\/span><\/span><\/p>\n

(A)<\/b><\/span><\/span>\u00a040 segundos.<\/b><\/span><\/span><\/span><\/span><\/p>\n

(B)\u00a0<\/b><\/span><\/span>32 segundos.<\/b><\/span><\/span><\/span><\/span><\/p>\n

(C)\u00a0<\/b><\/span><\/span>28 segundos.<\/b><\/span><\/span><\/span><\/span><\/p>\n

(D)\u00a0<\/b><\/span><\/span>16 segundos.<\/b><\/span><\/span><\/span><\/span><\/p>\n

(E)\u00a0<\/b><\/span><\/span>8 segundos.<\/b><\/span><\/span><\/span><\/span><\/p>\n

Na\u00a0<\/b><\/span><\/span>figura abaixo temos duas fotos sucessivas sendo uma tirada quando a vant est\u00e1 no ponto A<\/b><\/span><\/span>\u00a0e a\u00a0<\/b><\/span><\/span>outra quando est\u00e1 no ponto B,<\/b><\/span><\/span>\u00a0<\/b><\/span><\/span>separados por um intervalo de tempo e distantes d\u2019 entre si.<\/b><\/span><\/span><\/span><\/span><\/p>\n

Para facilitar\u00a0<\/b><\/span><\/span>vamos primeiro achar a dist\u00e2ncia d\u2019 percorrida pela vant entre essas duas posi\u00e7\u00f5es supondo que\u00a0n\u00e3o tenha havido sobreposi\u00e7\u00e3o frontal (figura abaixo).<\/b><\/span><\/span><\/span><\/span><\/p>\n

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R- B<\/b><\/span><\/span><\/span><\/span><\/span><\/span><\/p>\n

02-<\/b><\/span><\/span><\/span> <\/b>(ENEM-MEC-018)<\/b><\/span><\/span><\/span><\/span><\/span><\/h4>\n

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R- A<\/b><\/span><\/span><\/span><\/p>\n

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03-<\/b><\/span><\/span><\/span> <\/b>(ENEM-MEC-017)<\/b><\/span><\/span><\/span><\/span><\/span><\/h4>\n

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Em um\u00a0<\/b><\/span><\/span>telef\u00e9rico tur\u00edstico,<\/b><\/span><\/span>\u00a0<\/b><\/span><\/span>bondinhos saem de esta\u00e7\u00f5es ao n\u00edvel do mar<\/b><\/span><\/span>\u00a0e do\u00a0<\/b><\/span><\/span>topo de uma montanha.\u00a0<\/b><\/span><\/span>A\u00a0<\/b><\/span><\/span>travessia dura 1,5 minuto\u00a0<\/b><\/span><\/span>e\u00a0<\/b><\/span><\/span>ambos os bondinhos se deslocam \u00e0 mesma velocidade.<\/b><\/span><\/span><\/span><\/span><\/p>\n

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Quarenta segundos ap\u00f3s o bondinho A partir da esta\u00e7\u00e3o ao n\u00edvel do mar,<\/b><\/span><\/span>\u00a0ele\u00a0<\/b><\/span><\/span>cruza com o bondinho B, que havia sa\u00eddo do topo da montanha.<\/b><\/span><\/span><\/span><\/span><\/p>\n

Quantos segundos ap\u00f3s a partida do bondinho B partiu o bondinho A?<\/b><\/span><\/span><\/span><\/span><\/p>\n

(a)\u00a0<\/b><\/span><\/span>5.\u00a0<\/b><\/span><\/span>(b)\u00a0<\/b><\/span><\/span>10.\u00a0<\/b><\/span><\/span>(c)\u00a0<\/b><\/span><\/span>15.\u00a0<\/b><\/span><\/span>(d)\u00a0<\/b><\/span><\/span>20.\u00a0<\/b><\/span><\/span>(e)\u00a0<\/b><\/span><\/span>25<\/b><\/span><\/span><\/span><\/span><\/p>\n

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Se\u00a0<\/b><\/span><\/span>at\u00e9 o encontro A se moveu durante 40 s\u00a0<\/b><\/span><\/span>e\u00a0<\/b><\/span><\/span>B durante 50s,\u00a0<\/b><\/span><\/span>ent\u00e3o\u00a0<\/b><\/span><\/span>B partiu 10 s depois de A.<\/b><\/span><\/span><\/span><\/span><\/p>\n

R- B<\/b><\/span><\/span><\/span><\/span><\/p>\n

Ou,\u00a0<\/b><\/span><\/span>simples racioc\u00ednio:\u00a0<\/b><\/span><\/span>Se, quando eles se\u00a0<\/b><\/span><\/span>encontram A se moveu durante 40 s,\u00a0<\/b><\/span><\/span>ent\u00e3o com a\u00a0<\/b><\/span><\/span>mesma velocidade, B se moveu durante\u00a0<\/b><\/span><\/span>(90 \u2013 40 =\u00a0<\/b><\/span><\/span>50 s<\/b><\/span><\/span>) o que significa que\u00a0<\/b><\/span><\/span>B partiu 10 segundos depois de A<\/b><\/span><\/span><\/span><\/span><\/p>\n

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04<\/b><\/span><\/span><\/span>– <\/b><\/span><\/span><\/span>(ENEM-MEC-017)<\/b><\/span><\/span><\/span><\/span><\/span><\/h4>\n

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Movimento Circular Uniforme (MCU)<\/span><\/span><\/span><\/p>\n

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05<\/b><\/span><\/span><\/span>– <\/b><\/span><\/span><\/span>(ENEM-MEC-017)<\/b><\/span><\/span><\/span><\/span><\/h3>\n

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Piv\u00f4 central\u00a0<\/b><\/span><\/span>\u00e9 um\u00a0<\/b><\/span><\/span>sistema de irriga\u00e7\u00e3o muito usado na agricultura,<\/b><\/span><\/span>\u00a0em que uma\u00a0<\/b><\/span><\/span>\u00e1rea circular\u00a0<\/b><\/span><\/span>\u00e9\u00a0<\/b><\/span><\/span>projetada para receber uma estrutura suspensa.<\/b><\/span><\/span><\/span><\/span><\/p>\n

No\u00a0<\/b><\/span><\/span>centro dessa \u00e1rea, h\u00e1 uma tubula\u00e7\u00e3o vertical que transmite \u00e1gua atrav\u00e9s de um cano horizontal longo,\u00a0<\/b><\/span><\/span>apoiado em\u00a0<\/b><\/span><\/span>torres de sustenta\u00e7\u00e3o,\u00a0<\/b><\/span><\/span>as quais\u00a0<\/b><\/span><\/span>giram, sobre rodas, em torno do centro do piv\u00f4,\u00a0<\/b><\/span><\/span>tamb\u00e9m\u00a0<\/b><\/span><\/span>chamado de base,\u00a0<\/b><\/span><\/span>conforme mostram\u00a0<\/b><\/span><\/span>as figuras.<\/b><\/span><\/span><\/span><\/span><\/p>\n

Cada torre move-se com velocidade constante.<\/b><\/span><\/span><\/span><\/span><\/p>\n

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Um piv\u00f4 de tr\u00eas torres (T1, T2\u00a0e T3) ser\u00e1 instalado\u00a0<\/b><\/span><\/span>em uma fazenda,\u00a0<\/b><\/span><\/span>sendo que as dist\u00e2ncias entre torres consecutivas bem como da base \u00e0 torre T1\u00a0s\u00e3o iguais a 50 m.<\/b><\/span><\/span><\/span><\/span><\/p>\n

O fazendeiro pretende\u00a0<\/b><\/span><\/span>ajustar as velocidades das torres, de tal forma que o piv\u00f4 efetue uma volta completa em 25 horas.\u00a0<\/b><\/span><\/span>Use\u00a0<\/b><\/span><\/span>3 como aproxima\u00e7\u00e3o para \u03c0.<\/b><\/span><\/span><\/span><\/span><\/p>\n

Para\u00a0<\/b><\/span><\/span>atingir seu objetivo,\u00a0<\/b><\/span><\/span>as\u00a0<\/b><\/span><\/span>velocidades das torres T1,\u00a0T2\u00a0e\u00a0T3\u00a0devem ser, em metro por hora<\/b><\/span><\/span>, de<\/b><\/span><\/span><\/span><\/span><\/p>\n

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Trata-se de um\u00a0<\/b><\/span><\/span>movimento circular uniforme (MCU) cuja equa\u00e7\u00e3o da velocidade est\u00e1 definida abaixo:<\/b><\/span><\/span><\/span><\/span><\/p>\n

Como o\u00a0<\/b><\/span><\/span>piv\u00f4 deve efetuar uma volta completa a cada 25 h\u00a0<\/b><\/span><\/span>o\u00a0<\/b><\/span><\/span>per\u00edodo do piv\u00f4 e de cada uma das torres que o acompanha em seu movimento \u00e9 de T1\u00a0= T2\u00a0= T3\u00a0= 25h.<\/b><\/span><\/span><\/span><\/span><\/p>\n

Se as dist\u00e2ncias entre torres consecutivas bem como da base \u00e0 torre T1\u00a0s\u00e3o iguais a 50 m, voc\u00ea tem R1\u00a0= 50m, R2\u00a0= 100 m e R3\u00a0= 150m.<\/b><\/span><\/span><\/span><\/span><\/p>\n

Torre 1\u00a0\u00a0V1\u00a0=\u00a0<\/b><\/span><\/span>\u00a0<\/b><\/span><\/span>=\u00a0\u00a0=\u00a0\u00a0\u00a0<\/b><\/span><\/span>V1\u00a0= 12 m\/h.<\/b><\/span><\/span><\/span><\/span><\/p>\n

Torre 2\u00a0\u00a0V2\u00a0=\u00a0<\/b><\/span><\/span>\u00a0<\/b><\/span><\/span>=\u00a0\u00a0=\u00a0\u00a0\u00a0<\/b><\/span><\/span>V1\u00a0= 24 m\/h.<\/b><\/span><\/span><\/span><\/span><\/p>\n

Torre 3\u00a0\u00a0V1\u00a0=\u00a0<\/b><\/span><\/span>\u00a0<\/b><\/span><\/span>=\u00a0\u00a0=\u00a0\u00a0\u00a0<\/b><\/span><\/span>V1\u00a0= 36 m\/h.<\/b><\/span><\/span><\/span><\/span><\/p>\n

R- A<\/b><\/span><\/span><\/span><\/span><\/p>\n

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06<\/b><\/span><\/span><\/span>– <\/b><\/span><\/span><\/span>(ENEM-MEC-017)<\/b><\/span><\/span><\/span><\/span><\/span><\/p>\n

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Durante um\u00a0<\/b><\/span><\/span>passeio<\/b><\/span><\/span>\u00a0em uma\u00a0<\/b><\/span><\/span>bicicleta desse tipo, deseja-se\u00a0<\/b><\/span><\/span>fazer um\u00a0<\/b><\/span><\/span>percurso o mais devagar poss\u00edvel,\u00a0<\/b><\/span><\/span>escolhendo,\u00a0<\/b><\/span><\/span>para isso, uma das seguintes combina\u00e7\u00f5es de engrenagens (coroa x catraca):<\/b><\/span><\/span><\/span><\/span><\/p>\n

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A\u00a0<\/b><\/span><\/span>combina\u00e7\u00e3o escolhida para realizar esse passeio da forma desejada\u00a0<\/b><\/span><\/span>\u00e9<\/b><\/span><\/span><\/span><\/span><\/p>\n

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Basta\u00a0<\/b><\/span><\/span><\/span>prestar aten\u00e7\u00e3o no enunciado\u00a0<\/b><\/span><\/span><\/span>que afirma que o\u00a0<\/b><\/span><\/span><\/span>n\u00famero de voltas efetuadas pela roda traseira a cada pedalada \u00e9 calculado dividindo-se a quantidade de dentes da coroa pela quantidade de dentes da catraca\u00a0<\/b><\/span><\/span><\/span>e, fazendo isso voc\u00ea\u00a0<\/b><\/span><\/span><\/span>obt\u00e9m a tabela abaixo:<\/b><\/span><\/span><\/span><\/p>\n

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Voc\u00ea\u00a0<\/b><\/span><\/span><\/span>deve escolher a menor raz\u00e3o<\/b><\/span><\/span><\/span>\u00a0que \u00e9 aquela em que\u00a0<\/b><\/span><\/span><\/span>a roda traseira percorre a menor dist\u00e2ncia para fazer o percurso o mais devagar poss\u00edvel, fornecida pela alternativa IV.<\/b><\/span><\/span><\/span><\/p>\n

R \u2013 D<\/b><\/span><\/span><\/span><\/p>\n

Movimento Uniformemente Variado (MUV)<\/span><\/span><\/span><\/p>\n

07<\/b><\/span><\/span><\/span>– <\/b><\/span><\/span><\/span>(ENEM-MEC-017)<\/b><\/span><\/span><\/span><\/span><\/span><\/p>\n

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08<\/b><\/span><\/span><\/span>– <\/b><\/span><\/span><\/span>(ENEM-MEC-017)<\/b><\/span><\/span><\/span><\/span><\/span><\/h4>\n

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\"CINEMATICA\"<\/p>\n

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CINEMATICA<\/p>\n

Clique aqui para ver sobre o tema!<\/a><\/p>\n

Confira as v\u00eddeo aulas!<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"

MEC\u00c2NICA Cinem\u00e1tica Movimento Uniforme (MU) 01- (ENEM-MEC-019) A agricultura de precis\u00e3o re\u00fane t\u00e9cnicas agr\u00edcolas que consideram particularidades locais do solo ou lavoura a fim de otimizar o uso de recursos. Uma das formas de adquirir informa\u00e7\u00f5es sobre essas particularidades\u00a0\u00e9 a\u00a0fotografia a\u00e9rea de baixa altitude realizada por um ve\u00edculo a\u00e9reo n\u00e3o tripulado\u00a0(vant). Na\u00a0fase de aquisi\u00e7\u00e3o \u00e9 importante determinar o n\u00edvel de<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":3575,"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-5613","page","type-page","status-publish","hentry"],"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/pages\/5613","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=5613"}],"version-history":[{"count":3,"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/pages\/5613\/revisions"}],"predecessor-version":[{"id":9747,"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/pages\/5613\/revisions\/9747"}],"up":[{"embeddable":true,"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/pages\/3575"}],"wp:attachment":[{"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/media?parent=5613"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}