{"id":408,"date":"2015-02-08T14:48:19","date_gmt":"2015-02-08T14:48:19","guid":{"rendered":"http:\/\/fisicaevestibular.com.br\/novo\/?page_id=408"},"modified":"2024-09-03T13:17:43","modified_gmt":"2024-09-03T13:17:43","slug":"resolucao-comentada-do-enem-2014","status":"publish","type":"page","link":"https:\/\/fisicaevestibular.com.br\/novo\/universidades-2015\/exercicios-resolvidos-do-enem-2014\/resolucao-comentada-do-enem-2014\/","title":{"rendered":"Resolu\u00e7\u00e3o comentada do ENEM 2014"},"content":{"rendered":"

RESOLU\u00c7\u00d5ES<\/span><\/span><\/span><\/p>\n

01- <\/span><\/span><\/span>Todo <\/b><\/span><\/span><\/span>filtro <\/b><\/span><\/span><\/span>ressalta a pr\u00f3pria cor e diminui a cor oposta<\/b><\/span><\/span><\/span>.<\/b><\/span><\/span><\/span>.<\/span><\/span><\/span>A resposta est\u00e1 contida no enunciado, se tem <\/b><\/span><\/span><\/span>excesso de verde, para equilibra<\/b><\/span><\/span><\/span>r, ou seja, procurar manter as cores origiais, tem que<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

reduzir a passagem de verde<\/b><\/span><\/span><\/span>, ou seja, <\/b><\/span><\/span><\/span>permitir mais os vermelhos e azuis <\/b><\/span><\/span><\/span>(ou magenta)<\/b><\/span><\/span><\/span>, o \u00fanico que n\u00e3o tem a cor verde, para n\u00e3o real\u00e7\u00e1-la.<\/b><\/span><\/span><\/span>
\n<\/b><\/span><\/span><\/span>R- D<\/b><\/span><\/span><\/span><\/p>\n

02- <\/span><\/span><\/span>A <\/b><\/span><\/span>melhor lente<\/b><\/span><\/span><\/span> seria aquela que responde <\/b><\/span><\/span><\/span>mais rapidamente ao ambiente esterno<\/b><\/span><\/span><\/span>, se adaptandoa ele, ou seja, <\/b><\/span><\/span><\/span>deve possuir:<\/b><\/span><\/span><\/span><\/p>\n

(ii)<\/b><\/span><\/span><\/span>menor tempo<\/b><\/span><\/span><\/span> de <\/b><\/span><\/span>escurecimento quando exposta \u00e0 luz solar<\/b><\/span><\/span><\/span>(escurecer bem r\u00e1pido).<\/b><\/span><\/span><\/span><\/p>\n

(iii)<\/b><\/span><\/span><\/span>menor tempo<\/b><\/span><\/span><\/span>de <\/b><\/span><\/span>esmaecimento em ambiente sem forte luz solar<\/b><\/span><\/span><\/span>(clarear bem r\u00e1pido).<\/b><\/span><\/span><\/span><\/p>\n

Alem disso<\/b><\/span><\/span> (i)<\/b><\/span><\/span><\/span>pede que haja um maior escurecimento da lente<\/b><\/span><\/span><\/span> (<\/b><\/span><\/span>maior tempo de escurecimento), <\/b><\/span><\/span><\/span>o que <\/b><\/span><\/span>significa que a quantidade de luz que atravessa a lente <\/b><\/span><\/span><\/span>deve ser menor<\/b><\/span><\/span><\/span> que a quantidadede luz que incide<\/b><\/span><\/span><\/span>, <\/b><\/span><\/span>implicando numa menor transmit\u00e2ncia, o que ocorre com as amostras 3 e 4.<\/b><\/span><\/span><\/span><\/p>\n

Como a <\/b><\/span><\/span>melhor lente<\/b><\/span><\/span><\/span> a ser escolhida deve <\/b><\/span><\/span><\/span>reagir mais rapidamente ao ambiente externo<\/b><\/span><\/span><\/span> (tanto para o tempo de escurecimento como para o tempo de esmaecimento), voc\u00ea deve escolher a <\/b><\/span><\/span><\/span>amostra 3<\/b><\/span><\/span><\/span>, porque nela, a <\/b><\/span><\/span><\/span>soma dos tempos de esmaecimento e de escurecimento \u00e9 menor que na amostra 4.<\/b><\/span><\/span><\/span><\/p>\n

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

03- <\/b><\/span><\/span><\/span>Lei de Snell-Descartes<\/b><\/span><\/span><\/span><\/p>\n

\u201cA rela\u00e7\u00e3o entre o <\/b><\/span><\/span><\/span>seno do \u00e2ngulo de incid\u00eancia e o seno do \u00e2ngulo de refra\u00e7\u00e3o<\/b><\/span><\/span><\/span> \u00e9 uma <\/b><\/span><\/span><\/span>grandeza constante<\/b><\/span><\/span><\/span> denominada <\/b><\/span><\/span><\/span>\u00edndice de refra\u00e7\u00e3o do segundo meio em rela\u00e7\u00e3o ao primeiro<\/b><\/span><\/span><\/span>, ou seja,\u00a0 <\/b><\/span><\/span><\/span>seni\/senr=n<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span>\/n<\/b><\/span><\/span><\/span>1<\/b><\/span><\/span><\/sub><\/span>\u201d<\/b><\/span><\/span><\/span>\u00a0\u00a0<\/b><\/span><\/span><\/sub><\/span><\/p>\n

\"\"<\/p>\n

As <\/b><\/span><\/span><\/span>express\u00f5es acima nos mostram<\/b><\/span><\/span><\/span><\/span> que <\/b><\/span><\/span><\/span>quando a luz passar de um meio <\/b><\/span><\/span><\/span><\/span>menos refringente<\/b><\/span><\/span><\/span><\/span> (menor indice de refra\u00e7\u00e3o) para um meio <\/b><\/span><\/span><\/span><\/span>mais refringente<\/b><\/span><\/span><\/span><\/span> (maior \u00edndice de refra\u00e7\u00e3o<\/b><\/span><\/span><\/span><\/span>), o <\/b><\/span><\/span><\/span>\u00e2ngulo derefra\u00e7\u00e3o ser\u00e1 menor que o \u00e2ngulo de incid\u00eancia<\/b><\/span><\/span><\/span><\/span>(ele se aproxima da normal)<\/b><\/span><\/span><\/span><\/span> e menor ser\u00e1 a velocidade da luz nele. (figuras abaixo)<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

Pelo <\/b><\/span><\/span>princ\u00edpio da reversibilidade<\/b><\/span><\/span><\/span> (caminho inverso), quando a <\/b><\/span><\/span>luz passa de um meio mais refringente para um menos refringente sua velocidade aumenta e ele se afasta da normal.<\/b><\/span><\/span><\/span><\/p>\n

No caso do exerc\u00edcio:<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

\"\"<\/p>\n

r\u2019 < r<\/b><\/span><\/span><\/span>(o raio refratado se aproxima mais da normal)<\/b><\/span><\/span><\/span><\/p>\n

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

04- <\/span><\/span><\/span>Nas <\/b><\/span><\/span>usinas termonucleares \u00e9 utilizada a <\/b><\/span><\/span><\/span>fiss\u00e3o nuclear<\/b><\/span><\/span><\/span>que acontece quando um \u00e1tomo <\/b><\/span><\/span>(geralmente de<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>ur\u00e2nio<\/b><\/span><\/span><\/span><\/a>\u00a0<\/b><\/span><\/span><\/span>U-235)<\/b><\/span><\/span><\/span> \u00e9 bombardeado com n\u00eautrons, processo que libera uma <\/b><\/span><\/span>imensa quantidade de energia sob forma de calor que ir\u00e1 aquecer a \u00e1gua que fica dentro do reator transformando-a em vapor que pode chegar at\u00e9 a 320<\/b><\/span><\/span><\/span>o<\/b><\/span><\/span><\/sup><\/span>C.<\/b><\/span><\/span><\/span><\/p>\n

Esse <\/b><\/span><\/span>vapor tem por fun\u00e7\u00e3o movimentar as p\u00e1s das turbinas e gir\u00e1-las<\/b><\/span><\/span><\/span>,ocorrendo ent\u00e3o a <\/b><\/span><\/span>transforma\u00e7\u00e3o de energia t\u00e9rmica em energia mec\u00e2nica de rota\u00e7\u00e3o<\/b><\/span><\/span><\/span>. <\/b><\/span><\/span>O <\/b><\/span><\/span><\/span>eixo da turbinacomunica-se com um gerador, que transforma a <\/b><\/span><\/span><\/span>energia mec\u00e2nica em energia el\u00e9trica.<\/b><\/span><\/span><\/span><\/p>\n

Acontece que esse <\/b><\/span><\/span><\/span>vapor deve ser resfriado para se condensar<\/b><\/span><\/span><\/span>e se <\/b><\/span><\/span><\/span>transformar novamente em<\/b><\/span><\/span><\/span>\u00e1gua l\u00edquida<\/b><\/span><\/span><\/span> e, para isso, \u00e9 <\/b><\/span><\/span><\/span>utilizada a \u00e1gua de lagos, rios e mares<\/b><\/span><\/span><\/span>, \u00e0s margens dos quais a usina \u00e9 constru\u00edda, que <\/b><\/span><\/span><\/span>recebem calor do vapor para resfri\u00e1-lo e se aquecem<\/b><\/span><\/span><\/span>, <\/b><\/span><\/span><\/span>retornando ao ambiente com temperatura bem mais elevada.<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

Com esse <\/b><\/span><\/span><\/span>aquecimento a temperatura desses lagos, rios e mares tornam essas \u00e1guasimpr\u00f3prias,<\/b><\/span><\/span><\/span>diminuindoa solubilidade do oxig\u00eanio<\/b><\/span><\/span><\/span> e pondo em risco as diversas formas de vida aqu\u00e1tica que dependem desse g\u00e1s.<\/b><\/span><\/span><\/span><\/p>\n

Portanto, esse tipo de polui\u00e7\u00e3o est\u00e1 associado <\/b><\/span><\/span><\/span>\u00e0 condensa\u00e7\u00e3o do vapor-d\u2019\u00e1gua no final do processo.<\/b><\/span><\/span><\/span><\/p>\n

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

05- <\/span><\/span><\/span>O <\/b><\/span><\/span><\/span>corpo humano<\/b><\/span><\/span><\/span>, que apresenta uma <\/b><\/span><\/span><\/span>temperatura m\u00e9dia de 37<\/b><\/span><\/span><\/span>o<\/b><\/span><\/span><\/sup><\/span>C (310K),<\/b><\/span><\/span><\/span>pr\u00f3ximo \u00e0sencontradas no ambiente<\/b><\/span><\/span><\/span>, emite radia\u00e7\u00f5es, cujo <\/b><\/span><\/span><\/span>comprimento de onda<\/b><\/span><\/span><\/span>encontra-se em torno do<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

valor de <\/b><\/span><\/span><\/span>10<\/b><\/span><\/span><\/span>-5<\/b><\/span><\/span><\/sup><\/span> metros, freq\u00fc\u00eancia da ordem de10<\/b><\/span><\/span><\/span>13 <\/b><\/span><\/span><\/sup><\/span>Hz<\/b><\/span><\/span><\/span> e que est\u00e3o na <\/b><\/span><\/span><\/span>faixa dos infravermelhos<\/b><\/span><\/span><\/span>.<\/b><\/span><\/span><\/span><\/p>\n

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

06- <\/span><\/span><\/span>Como foi obtido o sentido da corrente el\u00e9trica da figura:<\/b><\/span><\/span><\/span><\/p>\n

O <\/b><\/span><\/span>p\u00f3lo norte<\/b><\/span><\/span><\/span> do im\u00e3 se <\/b><\/span><\/span><\/span>afasta da espira ou do solen\u00f3ide<\/b><\/span><\/span><\/span><\/p>\n

A <\/b><\/span><\/span>corrente induzida<\/b><\/span><\/span><\/span>na espira ou no solen\u00f3ide deve ter um <\/b><\/span><\/span><\/span>sentido <\/b><\/span><\/span><\/span>que vai originar na espira um <\/b><\/span><\/span><\/span>p\u00f3lo que deve atrair p\u00f3lo norte que se afasta<\/b><\/span><\/span><\/span> para impedir o afastamento.<\/b><\/span><\/span><\/span><\/p>\n

Assim, a <\/b><\/span><\/span>face esquerda da espira deve ser um p\u00f3lo sul.<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

Sabendo que a <\/b><\/span><\/span>face <\/b><\/span><\/span><\/span>esquerda<\/b><\/span><\/span><\/span> da espira ou solen\u00f3ide \u00e9 um <\/b><\/span><\/span><\/span>p\u00f3lo sul<\/b><\/span><\/span><\/span>(onde chegam as linhas deindu\u00e7\u00e3o)<\/b><\/span><\/span><\/span> e a face <\/b><\/span><\/span>direita<\/b><\/span><\/span><\/span> \u00e9 um <\/b><\/span><\/span>p\u00f3lo norte<\/b><\/span><\/span><\/span>(de onde saem as linhas de indu\u00e7\u00e3o<\/b><\/span><\/span><\/span>), aplica-se a regra <\/b><\/span><\/span>da m\u00e3o direita<\/b><\/span><\/span><\/span>(polegar no sentido da corrente e a \u201cfechada\u201d da m\u00e3o passando por dentro da espira, fornece o sentido das linhas de indu\u00e7\u00e3o).<\/b><\/span><\/span><\/span><\/p>\n

Assim, <\/b><\/span><\/span>para que a <\/b><\/span><\/span><\/span>face esquerda da espira seja um p\u00f3lo sul e a direita um p\u00f3lo norte<\/b><\/span><\/span><\/span>, a <\/b><\/span><\/span><\/span>corrente el\u00e9trica induzida deve ter o sentido das figuras acima.<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span><\/p>\n

Outra maneira de voc\u00ea obter o mesmo sentido para a corrente el\u00e9trica<\/b><\/span><\/span><\/span>:<\/p>\n

O <\/b><\/span><\/span>p\u00f3lo sul<\/b><\/span><\/span><\/span>do im\u00e3 se<\/b><\/span><\/span><\/span>aproxima da espira ou do solen\u00f3ide<\/b><\/span><\/span><\/span><\/p>\n

A <\/b><\/span><\/span>corrente induzida<\/b><\/span><\/span><\/span> deve ter um <\/b><\/span><\/span><\/span>sentido <\/b><\/span><\/span><\/span>que vai originar na espira <\/b><\/span><\/span><\/span>um p\u00f3lo que deve repelir p\u00f3losul que se aproxima<\/b><\/span><\/span><\/span>, na tentativa de impedir a aproxima\u00e7\u00e3o.<\/b><\/span><\/span><\/span><\/p>\n

Assim, a <\/b><\/span><\/span>face esquerda da espira deve ser um p\u00f3lo sul.<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

Sabendo que <\/b><\/span><\/span>a face esquerda da espira \u00e9 um p\u00f3lo sul<\/b><\/span><\/span><\/span>(onde chegam as linhas de indu\u00e7\u00e3o)<\/b><\/span><\/span><\/span> e que a <\/b><\/span><\/span>face direita \u00e9 um p\u00f3lo norte<\/b><\/span><\/span><\/span>(de onde saem as linhas de indu\u00e7\u00e3o),<\/b><\/span><\/span><\/span>aplica-se a <\/b><\/span><\/span>regra da m\u00e3odireita(polegar no sentido da corrente e a \u201cfechada\u201d da m\u00e3o passando por dentro da espira, fornece o sentido das linhas de indu\u00e7\u00e3o).<\/b><\/span><\/span><\/span><\/p>\n

Assim, para que a <\/b><\/span><\/span>face esquerda da espira seja um p\u00f3lo sul e a direita um p\u00f3lo norte<\/b><\/span><\/span><\/span>, a <\/b><\/span><\/span>correnteel\u00e9trica induzida<\/b><\/span><\/span><\/span>deve ter o sentido das figuras acima que \u00e9 o mesmo que da figura do enunciado.<\/b><\/span><\/span><\/span><\/p>\n

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

07-<\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

\"\"<\/p>\n

08- <\/span><\/span><\/span>Altura do som<\/b><\/span><\/span><\/span> est\u00e1 relacionada com sua <\/b><\/span><\/span>freq\u00fc\u00eancia,<\/b><\/span><\/span><\/span> ou seja, a <\/b><\/span><\/span>altura (tom)<\/b><\/span><\/span><\/span> \u00e9 a <\/b><\/span><\/span>qualidade do som que permite ao ouvido distinguir um som grave, de baixa frequ\u00eancia, de um som agudo, de alta<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

freq\u00fc\u00eancia.<\/b><\/span><\/span><\/span>\u00a0 Cada <\/b><\/span><\/span>nota musical (tom)<\/b><\/span><\/span><\/span> possui <\/b><\/span><\/span>frequ\u00eancia caracter\u00edstica, \u00fanica para essa nota.<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/p>\n

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

09- <\/span><\/span><\/span>P\u00eandulo Simples:<\/b><\/span><\/span><\/span>\u00a0consta de uma <\/b><\/span><\/span>massa m,<\/b><\/span><\/span><\/span> <\/b>presa na extremidade inferior de um fio ideal<\/b><\/span><\/span><\/span>, <\/b><\/span><\/span>fixada verticalmente<\/b><\/span><\/span><\/span> na sua <\/b><\/span><\/span>extremidade superior<\/b><\/span><\/span><\/span> (figura)\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0<\/b><\/span><\/span><\/p>\n

\"\"<\/p>\n

Se o <\/b><\/span><\/span><\/span>p\u00eandulo simples<\/b><\/span><\/span><\/span> oscilar, com oscila\u00e7\u00f5es de pequena abertura <\/b><\/span><\/span><\/span>(no m\u00e1ximo 15<\/b><\/span><\/span><\/span>o<\/b><\/span><\/span><\/sup><\/span>)<\/b><\/span><\/span><\/span>, ele descreve um <\/b><\/span><\/span><\/span>movimento circular de raio R=L, sendo L o comprimento do fio.<\/b><\/span><\/span><\/span><\/p>\n

Seu <\/b><\/span><\/span><\/span>per\u00edodo (T)<\/b><\/span><\/span><\/span>, que \u00e9 o <\/b><\/span><\/span><\/span>tempo que ele demora para efetuar um \u201cvai e vem\u201d completo \u00e9 fornecido pela express\u00e3o:<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

onde <\/b><\/span><\/span><\/span>g \u00e9 a acelera\u00e7\u00e3o da gravidade local.<\/b><\/span><\/span><\/span><\/p>\n

Observe que:<\/b><\/span><\/span><\/span><\/p>\n

* a <\/b><\/span><\/span><\/span>massa pendular m<\/b><\/span><\/span><\/span> n\u00e3o <\/b><\/span><\/span><\/span>influi no per\u00edodo T do movimento<\/b><\/span><\/span><\/span> <\/b>influindo apenas o comprimento L do<\/b><\/span><\/span><\/span> <\/b>p\u00eandulo, e a acelera\u00e7\u00e3o da gravidade local.<\/b><\/span><\/span><\/span> Assim, <\/b><\/span><\/span><\/span>dois p\u00eandulos de <\/b><\/span><\/span><\/span>mesmo comprimento L<\/b><\/span><\/span><\/span>, mas <\/b><\/span><\/span><\/span>de massas diferentes M e m, apresentam o mesmo per\u00edodo T.<\/b><\/span><\/span><\/span><\/p>\n

\u00a0* O <\/b><\/span><\/span><\/span>per\u00edodo <\/b><\/span><\/span><\/span>de um p\u00eandulo simples <\/b><\/span><\/span><\/span>independe da amplitude<\/b><\/span><\/span><\/span>, ou seja, da <\/b><\/span><\/span><\/span>altura em que m \u00e9<\/b><\/span><\/span><\/span> <\/b>abandonada<\/b><\/span><\/span><\/span>, assim, os <\/b><\/span><\/span><\/span>p\u00eandulos da figura abaixo, tanto na situa\u00e7\u00e3o 1 como na 2<\/b><\/span><\/span><\/span>, <\/b><\/span><\/span><\/span>demoram o mesmo tempo para ir de <\/b><\/span><\/span><\/span>A at\u00e9 B, de B at\u00e9 C, de C at\u00e9 B e de B at\u00e9 A.<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

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

10- <\/span><\/span><\/span>A <\/b><\/span><\/span><\/span>esta\u00e7\u00e3o emissora<\/b><\/span><\/span><\/span> de <\/b><\/span><\/span><\/span>ondas eletromagn\u00e9ticas<\/b><\/span><\/span><\/span> de r\u00e1dio, TV, etc, <\/b><\/span><\/span><\/span>geram essas ondas, de<\/b><\/span><\/span><\/span> <\/b>determinada freq\u00fc\u00eancia por meio osciladores eletr\u00f4nicos<\/b><\/span><\/span><\/span> e as <\/b><\/span><\/span><\/span>emitem at\u00e9 o aparelho receptor<\/b><\/span><\/span><\/span>, cujos el\u00e9trons entram em <\/b><\/span><\/span><\/span>resson\u00e2ncia <\/b><\/span><\/span><\/span>com a <\/b><\/span><\/span><\/span>onda eletromagn\u00e9tica emitida pela esta\u00e7\u00e3o emissora<\/b><\/span><\/span><\/span>, <\/b><\/span><\/span><\/span>oscilando com a <\/b><\/span><\/span><\/span>mesma freq\u00fc\u00eancia<\/b><\/span><\/span><\/span> por ela emitida, produzindo o sinal el\u00e9trico<\/b><\/span><\/span><\/span><\/p>\n

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

11- <\/span><\/span><\/span>Com a chave ligada em A<\/b><\/span><\/span><\/span><\/p>\n

Observe na <\/b><\/span><\/span>figura abaixo<\/b><\/span><\/span><\/span> que <\/b><\/span><\/span>n\u00e3o <\/b><\/span><\/span><\/span>circular\u00e1 corrente el\u00e9trica pela l\u00e2mpada 2 (figura).<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

C\u00e1lculo<\/b><\/span><\/span> da <\/b><\/span><\/span><\/span>resist\u00eancia<\/b><\/span><\/span><\/span> do <\/b><\/span><\/span><\/span>resistor equivalente<\/b><\/span><\/span><\/span> nas sequ\u00eancias abaixo:<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

\"\"<\/p>\n

Observe na figura abaixo<\/b><\/span><\/span><\/span> que a <\/b><\/span><\/span>corrente total i<\/b><\/span><\/span><\/span>1<\/b><\/span><\/span><\/sub><\/span> = 2U\/R<\/b><\/span><\/span><\/span> que sai do gerador, \u00e9 <\/b><\/span><\/span>dividida em cada um dos<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

ramos em <\/b><\/span><\/span><\/span>partes iguais<\/b><\/span><\/span><\/span>, pois as <\/b><\/span><\/span>l\u00e2mpadas 1 e 3 possuem a mesma resist\u00eancia R.<\/b><\/span><\/span><\/span><\/p>\n

Ent\u00e3o, as <\/b><\/span><\/span>l\u00e2mpadas 1 e 3 ter\u00e3o a <\/b><\/span><\/span><\/span>mesma corrente<\/b><\/span><\/span><\/span> valendo i<\/b><\/span><\/span><\/span>1<\/b><\/span><\/span><\/sub><\/span>\u2019 = i<\/b><\/span><\/span><\/span>3<\/b><\/span><\/span><\/sub><\/span>\u2019 = i<\/b><\/span><\/span><\/span>1<\/b><\/span><\/span><\/sub><\/span>\/2 = 2u\/2R = U\/R.<\/b><\/span><\/span><\/span><\/p>\n

Com a chave ligada em B<\/b><\/span><\/span><\/span><\/p>\n

Nesse caso,<\/b><\/span><\/span><\/span> <\/b>todas as <\/b><\/span><\/span><\/span>3 l\u00e2mpadas<\/b><\/span><\/span><\/span> ser\u00e3o percorridas por corrente el\u00e9trica:<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

A sequ\u00eancia abaixo mostra o c\u00e1lculo da <\/b><\/span><\/span><\/span>resist\u00eancia equivalente:<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

\"\"<\/p>\n

\"\"<\/p>\n

Observe que, pela <\/b><\/span><\/span><\/span>l\u00e2mpada 2<\/b><\/span><\/span><\/span> circular\u00e1 a corrente total <\/b><\/span><\/span><\/span>i<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span> = 2U\/3R.<\/b><\/span><\/span><\/span><\/p>\n

A <\/b><\/span><\/span><\/span>pot\u00eancia P da l\u00e2mpada est\u00e1 relacionada com o brilho, maior pot\u00eancia, maior brilho<\/b><\/span><\/span><\/span>, pois.<\/b><\/span><\/span><\/span><\/p>\n

como a <\/b><\/span><\/span><\/span>resist\u00eancia R \u00e9 a mesma<\/b><\/span><\/span><\/span> para cada l\u00e2mpada e <\/b><\/span><\/span><\/span>P = R.i<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sup><\/span>, a <\/b><\/span><\/span><\/span>pot\u00eancia P tamb\u00e9m \u00e9 diretamente proporcional a i.<\/b><\/span><\/span><\/span><\/p>\n

Maior corrente, maior brilho<\/b><\/span><\/span><\/span>.<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

Analise os <\/b><\/span><\/span><\/span>dois casos<\/b><\/span><\/span><\/span> nos esquemas das figuras abaixo e verifique que a <\/b><\/span><\/span><\/span>corrente na l\u00e2mpada 1 \u00e9 maior (maior brilho) com a chave ligada em A<\/b><\/span><\/span><\/span> <\/b>onde a <\/b><\/span><\/span><\/span>resist\u00eancia equivalente<\/b><\/span><\/span><\/span> \u00e9 R\/2 <\/b><\/span><\/span><\/span>menor que a<\/b><\/span><\/span><\/span> <\/b>de B<\/b><\/span><\/span><\/span>, que \u00e9 3R\/2.<\/b><\/span><\/span><\/span><\/p>\n

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

12- <\/span><\/span><\/span>O fato de o <\/b><\/span><\/span>enunciado afirmar<\/b><\/span><\/span><\/span> que, sobre a <\/b><\/span><\/span>extremidade superior do<\/b><\/span><\/span><\/span> <\/b>\u00eambolo<\/b><\/span><\/span><\/span>, que pode <\/b><\/span><\/span>movimentar-se livremente sem atrito, encontra-se um objeto, <\/b><\/span><\/span><\/span>significa que a transforma\u00e7\u00e3o \u00e9 isob\u00e1rica (press\u00e3o constante).<\/b><\/span><\/span><\/span><\/p>\n

Primeira lei da equa\u00e7\u00e3o geral dos gases perfeitos<\/b><\/span><\/span><\/span>:<\/b><\/span><\/span><\/span> <\/b>Para <\/b><\/span><\/span><\/span>uma quantidade de g\u00e1s constante a uma <\/b><\/span><\/span><\/span>dada press\u00e3o\u00a0<\/b><\/span><\/span><\/span>( transforma\u00e7\u00e3o isob\u00e1rica )<\/b><\/span><\/span><\/span>,<\/b><\/span><\/span><\/span> o <\/b><\/span><\/span><\/span>volume e a temperatura absoluta<\/b><\/span><\/span><\/span> de uma amostra gasosa <\/b><\/span><\/span><\/span>s\u00e3o <\/b><\/span><\/span>grandezas diretamente proporcionais<\/b><\/span><\/span><\/span>, ou seja, <\/b><\/span><\/span><\/span>\u2206V \u00e9 proporcional a \u2206T.<\/b><\/span><\/span><\/span><\/p>\n

Representa\u00e7\u00e3o gr\u00e1fica:<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

Observe na <\/b><\/span><\/span><\/span>lei ou na representa\u00e7\u00e3o gr\u00e1fica<\/b><\/span><\/span><\/span> que <\/b><\/span><\/span><\/span>um aumento ou diminui\u00e7\u00e3o na temperatura implica num <\/b><\/span><\/span><\/span>proporcional aumento ou diminui\u00e7\u00e3o do volume.<\/b><\/span><\/span><\/span><\/p>\n

A <\/b><\/span><\/span><\/span>capacidade calor\u00edfica C<\/b><\/span><\/span><\/span> de determinada amostra gasosa \u00e9 fornecida pela <\/b><\/span><\/span><\/span>express\u00e3o C = Q\/\u2206T,<\/b><\/span><\/span><\/span> onde <\/b><\/span><\/span><\/span>Q \u00e9 o calor absorvido<\/b><\/span><\/span><\/span> pelo g\u00e1s e <\/b><\/span><\/span><\/span>\u2206T<\/b><\/span><\/span><\/span> sua consequente varia\u00e7\u00e3o de temperatura<\/b><\/span><\/span><\/span>.<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

13- <\/span><\/span><\/span>Sendo a <\/b><\/span><\/span><\/span>colis\u00e3o el\u00e1stica a energia total (cin\u00e9tica do sistema constitu\u00eddo pelas 5 esferas) \u00e9 a mesma<\/b><\/span><\/span><\/span> <\/b>antes e depois do choque<\/b><\/span><\/span><\/span> e o <\/b><\/span><\/span><\/span>coeficiente de restitui\u00e7\u00e3o vale e=1<\/b><\/span><\/span><\/span>. Como em <\/b><\/span><\/span><\/span>todo em tipo de choque, a <\/b><\/span><\/span><\/span>quantidade de movimento do sistema tamb\u00e9m se conserva.<\/b><\/span><\/span><\/span><\/p>\n

Se voc\u00ea <\/b><\/span><\/span><\/span>chamar <\/b><\/span><\/span><\/span>de m a massa de cada esfera e de V sua respectiva velocidade<\/b><\/span><\/span><\/span>, o <\/b><\/span><\/span><\/span>m\u00f3dulo<\/b><\/span><\/span><\/span> da<\/b><\/span><\/span><\/span> <\/b>quantidade de movimento do sistema antes do choque<\/b><\/span><\/span><\/span> (com as 3 esferas se movendo para a direita) \u00e9 <\/b><\/span><\/span><\/span>Q<\/b><\/span><\/span><\/span>sa<\/b><\/span><\/span><\/sub><\/span> = mV + mV = mV <\/b><\/span><\/span><\/span>= 3mV.<\/b><\/span><\/span><\/span><\/p>\n

Assim, o <\/b><\/span><\/span><\/span>m\u00f3dulo da quantidade de movimento<\/b><\/span><\/span><\/span> do sistema <\/b><\/span><\/span><\/span>depois do choque deve ser tamb\u00e9m Q<\/b><\/span><\/span><\/span>sd<\/b><\/span><\/span><\/sub><\/span> =<\/b><\/span><\/span><\/span><\/b><\/p>\n

\"\"<\/p>\n

3mV <\/b><\/span><\/span><\/span>\u00e9 a \u00fanica alternativa que satisfaz \u00e9 a C.<\/b><\/span><\/span><\/span><\/p>\n

R- C.<\/b><\/span><\/span><\/span><\/p>\n

14- <\/span><\/span><\/span>Observe que no <\/b><\/span><\/span><\/span>terceiro quadrinho<\/b><\/span><\/span><\/span> o coelhinho est\u00e1 em <\/b><\/span><\/span><\/span>\u00f3rbita circular ao redor da Terra<\/b><\/span><\/span><\/span>, como<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

um sat\u00e9lite e, se <\/b><\/span><\/span><\/span>sua velocidade \u00e9 constante em m\u00f3dulo, n\u00e3o existe acelera\u00e7\u00e3o tangencial, que \u00e9 nula<\/b><\/span><\/span><\/span><\/p>\n

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

15- <\/span><\/span><\/span>Se voc\u00ea <\/b><\/span><\/span>reduzir o plano de inclina\u00e7\u00e3o a zero<\/b><\/span><\/span><\/span>, a <\/b><\/span><\/span>esfera estar\u00e1 se movendo num plano horizontal<\/b><\/span><\/span><\/span> e, <\/b><\/span><\/span>como <\/b><\/span><\/span><\/span>n\u00e3o existe atrito<\/b><\/span><\/span><\/span>, a <\/b><\/span><\/span><\/span>for\u00e7a resultante<\/b><\/span><\/span><\/span> sobre ela na dire\u00e7\u00e3o do movimento <\/b><\/span><\/span><\/span>ser\u00e1 nula (F<\/b><\/span><\/span><\/span>R<\/b><\/span><\/span><\/sub><\/span> = 0).<\/b><\/span><\/span><\/span><\/p>\n

O <\/b><\/span><\/span><\/span>impulso resultante<\/b><\/span><\/span><\/span> sobre ela vale <\/b><\/span><\/span><\/span>I = F<\/b><\/span><\/span><\/span>R<\/b><\/span><\/span><\/sub><\/span>.\u2206t<\/b><\/span><\/span><\/span> = 0.\u2206t <\/b><\/span><\/span><\/span>= 0.<\/b><\/span><\/span><\/span><\/p>\n

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

 <\/p>\n

Voltar para os Exerc\u00edcios do ENEM 2014<\/span><\/a><\/h3>\n","protected":false},"excerpt":{"rendered":"

RESOLU\u00c7\u00d5ES 01- Todo filtro ressalta a pr\u00f3pria cor e diminui a cor oposta..A resposta est\u00e1 contida no enunciado, se tem excesso de verde, para equilibrar, ou seja, procurar manter as cores origiais, tem que reduzir a passagem de verde, ou seja, permitir mais os vermelhos e azuis (ou magenta), o \u00fanico que n\u00e3o tem a cor verde, para n\u00e3o real\u00e7\u00e1-la.<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":407,"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-408","page","type-page","status-publish","hentry"],"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/pages\/408","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=408"}],"version-history":[{"count":2,"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/pages\/408\/revisions"}],"predecessor-version":[{"id":412,"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/pages\/408\/revisions\/412"}],"up":[{"embeddable":true,"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/pages\/407"}],"wp:attachment":[{"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/media?parent=408"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}