{"id":374,"date":"2015-01-08T02:49:33","date_gmt":"2015-01-08T02:49:33","guid":{"rendered":"http:\/\/fisicaevestibular.com.br\/novo\/?page_id=374"},"modified":"2024-09-02T16:43:38","modified_gmt":"2024-09-02T16:43:38","slug":"resolucao-comentada-da-famerp-2015","status":"publish","type":"page","link":"https:\/\/fisicaevestibular.com.br\/novo\/universidades-2015\/exercicios-da-famerp-2015\/resolucao-comentada-da-famerp-2015\/","title":{"rendered":"Resolu\u00e7\u00e3o comentada da FAMERP 2015"},"content":{"rendered":"

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

01- \"\"<\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

02-<\/span><\/span><\/span>) a) Observe na figura abaixo<\/b><\/span><\/span><\/span> que, depois que o objeto foi preso \u00e0 mola que estava em seu <\/b><\/span><\/span><\/span>comprimento natural de <\/b><\/span><\/span><\/span>20cm<\/b><\/span><\/span><\/span>,<\/b><\/span><\/span><\/span> ela foi <\/b><\/span><\/span><\/span>deformada<\/b><\/span><\/span><\/span> com seu<\/b><\/span><\/span><\/span>comprimento passando para <\/b><\/span><\/span><\/span>25cm<\/b><\/span><\/span><\/span> e<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

sofrendo uma <\/b><\/span><\/span><\/span>deforma\u00e7\u00e3o de \u2206x = 5cm = 0,05m<\/b><\/span><\/span><\/span>, quando atingiu a <\/b><\/span><\/span><\/span>situa\u00e7\u00e3o de equil\u00edbrio.<\/b><\/span><\/span><\/span><\/p>\n

Na <\/b><\/span><\/span><\/span>situa\u00e7\u00e3o de equil\u00edbrio<\/b><\/span><\/span><\/span>, as <\/b><\/span><\/span><\/span>for\u00e7as<\/b><\/span><\/span><\/span> que agem sobre o objeto s\u00e3o, seu <\/b><\/span><\/span><\/span>peso<\/b><\/span><\/span><\/span> (vertical e para baixo) e a <\/b><\/span><\/span><\/span>for\u00e7a el\u00e1stica<\/b><\/span><\/span><\/span> (vertical e para cima), que sustenta o objeto, que est\u00e1 em <\/b><\/span><\/span><\/span>equil\u00edbrio, mas n\u00e3o em repouso (for\u00e7a resultante sobre ele \u00e9 nula).<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

b)<\/b><\/span><\/span><\/span> <\/b>Suponha que o <\/b><\/span><\/span><\/span>objeto seja elevado <\/b><\/span><\/span><\/span>at\u00e9 a <\/b><\/span><\/span><\/span>altura em que o comprimento da mola volta a ser <\/b><\/span><\/span><\/span>20 cm<\/b><\/span><\/span><\/span> <\/b>e, em seguida, <\/b><\/span><\/span><\/span>solto<\/b><\/span><\/span><\/span> <\/b>a partir do repouso.<\/b><\/span><\/span><\/span> <\/b>Determine a <\/b><\/span><\/span><\/span>energia cin\u00e9tica<\/b><\/span><\/span><\/span> do objeto, em <\/b><\/span><\/span><\/span>joules<\/b><\/span><\/span><\/span>, no instante em que <\/b><\/span><\/span><\/span>passa pelo ponto em que o comprimento da mola \u00e9 de 25 cm<\/b><\/span><\/span><\/span>. Despreze qualquer perda de energia mec\u00e2nica.<\/b><\/span><\/span><\/span><\/p>\n

b) C\u00e1lculo da <\/b><\/span><\/span><\/span>energia mec\u00e2nica no ponto <\/b><\/span><\/span><\/span>P<\/b><\/span><\/span><\/span> onde, pelo enunciado <\/b><\/span><\/span><\/span>partiu do repouso <\/b><\/span><\/span><\/span>V<\/b><\/span><\/span><\/span>P<\/b><\/span><\/span><\/sub><\/span> = <\/b><\/span><\/span><\/span>0<\/b><\/span><\/span><\/span> e se encontra na <\/b><\/span><\/span><\/span>altura de h=0,05m<\/b><\/span><\/span><\/span> em rela\u00e7\u00e3o ao ponto Q tomado como referencial. Nesse ponto , a <\/b><\/span><\/span><\/span>mola est\u00e1 em sua posi\u00e7\u00e3o natural<\/b><\/span><\/span><\/span> e <\/b><\/span><\/span><\/span>n\u00e3o existe energia potencial el\u00e1stica armazenada<\/b><\/span><\/span><\/span>.<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

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

\"\"<\/p>\n

b)<\/b><\/span><\/span><\/span> <\/b>Que <\/b><\/span><\/span><\/span>volume de \u00e1lcool, em <\/b><\/span><\/span><\/span>cm<\/b><\/span><\/span><\/span>3<\/b><\/span><\/span><\/sup><\/span>, deve ser <\/b><\/span><\/span><\/span>misturado \u00e0 \u00e1gua<\/b><\/span><\/span><\/span> do recipiente para que o <\/b><\/span><\/span><\/span>topo do bloco passe a coincidir com a superf\u00edcie do l\u00edquido? A massa espec\u00edfica do \u00e1lcool \u00e9 <\/b><\/span><\/span><\/span>0,80 g\/cm<\/b><\/span><\/span><\/span>3<\/b><\/span><\/span><\/sup><\/span>.<\/b><\/span><\/span><\/span><\/p>\n

\"\"04- <\/span><\/span><\/span>a)<\/b><\/span><\/span><\/span> <\/b>Calcule a <\/b><\/span><\/span><\/span>dist\u00e2ncia focal<\/b><\/span><\/span><\/span> da lente, em cm.<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

\"\"<\/p>\n

Observa\u00e7\u00e3o: <\/b><\/span><\/span><\/span>Voc\u00ea poderia tamb\u00e9m, <\/b><\/span><\/span><\/span>na figura 2, tra\u00e7ar o seguinte raio not\u00e1vel<\/b><\/span><\/span><\/span> para localizar a lente:<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

\u201c Todo raio de luz que incide passando pelo centro \u00f3ptico da lente n\u00e3o sofre desvio\u201d.<\/b><\/span><\/span><\/span><\/p>\n

Na <\/b><\/span><\/span><\/span>figura acima esse raio corta o eixo principal<\/b><\/span><\/span><\/span>, <\/b><\/span><\/span><\/span>localizando a lente num ponto \u00e0 dist\u00e2ncia P = 80 cm do objeto.<\/b><\/span><\/span><\/span><\/p>\n

05-<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

b)<\/b><\/span><\/span><\/span> <\/b>Que <\/b><\/span><\/span><\/span>quantidade de \u00e1gua, a <\/b><\/span><\/span><\/span>95<\/b><\/span><\/span><\/span>o<\/b><\/span><\/span><\/sup><\/span>C<\/b><\/span><\/span><\/span>,<\/b><\/span><\/span><\/span> deve ser <\/b><\/span><\/span><\/span>colocada no calor\u00edmetro<\/b><\/span><\/span><\/span> para que a <\/b><\/span><\/span><\/span>temperatura final volte a ser de 80<\/b><\/span><\/span><\/span>o<\/b><\/span><\/span><\/sup><\/span>C?<\/b><\/span><\/span><\/span><\/p>\n

b) <\/b><\/span><\/span><\/span>Agora voc\u00ea tem no calor\u00edmetro o <\/b><\/span><\/span><\/span>bloco de concreto a <\/b><\/span><\/span><\/span>70<\/b><\/span><\/span><\/span>o<\/b><\/span><\/span><\/sup><\/span>C<\/b><\/span><\/span><\/span> e a \u00e1gua tamb\u00e9m a <\/b><\/span><\/span><\/span>70<\/b><\/span><\/span><\/span>o<\/b><\/span><\/span><\/sup><\/span>C<\/b><\/span><\/span><\/span> que v\u00e3o trocar calor com a <\/b><\/span><\/span><\/span>massa <\/b><\/span><\/span><\/span>m <\/b><\/span><\/span><\/span>de \u00e1gua a <\/b><\/span><\/span><\/span>95<\/b><\/span><\/span><\/span>o<\/b><\/span><\/span><\/sup><\/span>C<\/b><\/span><\/span><\/span> at\u00e9 que, <\/b><\/span><\/span><\/span>no final<\/b><\/span><\/span><\/span>, todos v\u00e3o ficar com a <\/b><\/span><\/span><\/span>mesma temperatura (de equil\u00edbrio t\u00e9rmico) de t<\/b><\/span><\/span><\/span>e<\/b><\/span><\/span><\/sub><\/span>\u2019=80<\/b><\/span><\/span><\/span>o<\/b><\/span><\/span><\/sup><\/span>C.<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

06- <\/b><\/span><\/span><\/span>a)<\/b><\/span><\/span><\/span> <\/b>Esquematize o circuito el\u00e9trico<\/b><\/span><\/span><\/span> que deve ser montado pelo eletricista <\/b><\/span><\/span><\/span>(n\u00e3o \u00e9 necess\u00e1rio desenhar todas as l\u00e2mpadas).<\/b><\/span><\/span><\/span><\/p>\n

Indique quantas l\u00e2mpadas h\u00e1 em cada grupo e como s\u00e3o associadas.<\/b><\/span><\/span><\/span> Indique tamb\u00e9m como os <\/b><\/span><\/span><\/span>grupos s\u00e3o associados para serem ligados \u00e0 rede el\u00e9trica.<\/b><\/span><\/span><\/span><\/p>\n

a) <\/b><\/span><\/span><\/span>Na <\/b><\/span><\/span><\/span>associa\u00e7\u00e3o s\u00e9rie a <\/b><\/span><\/span><\/span>corrente el\u00e9trica i<\/b><\/span><\/span><\/span> \u00e9 a mesma para cada l\u00e2mpada<\/b><\/span><\/span><\/span> e a <\/b><\/span><\/span><\/span>tens\u00e3o (ddp ou voltagem) U<\/b><\/span><\/span><\/span>total<\/b><\/span><\/span><\/sub><\/span> = 120V \u00e9 a soma das tens\u00f5es nominais de cada l\u00e2mpada que deve ser de U=12V para que cada uma funcione normalmente.<\/b><\/span><\/span><\/span><\/p>\n

Assim, voc\u00ea <\/b><\/span><\/span><\/span>deve ter n<\/b><\/span><\/span><\/span> = 120\/12=<\/b><\/span><\/span><\/span>10 l\u00e2mpadas<\/b><\/span><\/span><\/span> <\/b>associadas em s\u00e9rie<\/b><\/span><\/span><\/span> e funcionando normalmente em<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

um <\/b><\/span><\/span><\/span>\u00fanico ramo e ligadas em U<\/b><\/span><\/span><\/span>total<\/b><\/span><\/span><\/sub><\/span> =120V.<\/b><\/span><\/span><\/span><\/p>\n

Acontece que voc\u00ea <\/b><\/span><\/span><\/span>deve associar <\/b><\/span><\/span><\/span>200 l\u00e2mpadas<\/b><\/span><\/span><\/span> e, ent\u00e3o voc\u00ea deve ter uma <\/b><\/span><\/span><\/span>associa\u00e7\u00e3o paralelo de<\/b><\/span><\/span><\/span> <\/b>20 ramos <\/b><\/span><\/span><\/span>(20×10=200 l\u00e2mpadas), <\/b><\/span><\/span><\/span>pois a <\/b><\/span><\/span><\/span>caracter\u00edstica dessa associa\u00e7\u00e3o<\/b><\/span><\/span><\/span> \u00e9 que, nela <\/b><\/span><\/span><\/span>cada ramo possui tens\u00e3o de 120 V.<\/b><\/span><\/span><\/span><\/p>\n

Esquema do circuito:<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

Os <\/b><\/span><\/span><\/span>20 ramos de 10 l\u00e2mpadas em s\u00e9rie<\/b><\/span><\/span><\/span> devem ser <\/b><\/span><\/span><\/span>associados em paralelo<\/b><\/span><\/span><\/span> e ligados na tomada de <\/b><\/span><\/span><\/span>120V.<\/b><\/span><\/span><\/span><\/b><\/p>\n

\"\"<\/p>\n

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

\"\"<\/p>\n

08-<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

09- <\/b><\/span><\/span><\/span>Terceira lei de Kepler (lei dos per\u00edodos)<\/b><\/span><\/span><\/span><\/p>\n

\u00a0<\/span>\u201c Os <\/b><\/span><\/span><\/span>quadrados dos <\/b><\/span><\/span><\/span>per\u00edodos\u00a0T<\/b><\/span><\/span><\/span>\u00a0de revolu\u00e7\u00e3o dos planetas<\/b><\/span><\/span><\/span> (tempo que demora para efetuar uma volta completa em torno do Sol) <\/b><\/span><\/span><\/span>s\u00e3o <\/b><\/span><\/span><\/span>proporcionais<\/b><\/span><\/span><\/span> aos cubos das suas <\/b><\/span><\/span><\/span>dist\u00e2ncias m\u00e9dias R\u00a0ao Sol<\/b><\/span><\/span><\/span>\u201d<\/b><\/span><\/span><\/span><\/p>\n

T<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sup><\/span>\/R<\/b><\/span><\/span><\/span>3<\/b><\/span><\/span><\/sup><\/span>=constante=K\u2019<\/b><\/span><\/span><\/span><\/p>\n

O mesmo \u00e9 v\u00e1lido para Terra-Lua.<\/b><\/span><\/span><\/span> Se a <\/b><\/span><\/span><\/span>dist\u00e2ncia m\u00e9dia R da Lua \u00e0 Terra aumenta<\/b><\/span><\/span><\/span>, e ela \u00e9 <\/b><\/span><\/span><\/span>proporcional ao per\u00edodo de transla\u00e7\u00e3o da Lua ao redor da Terra<\/b><\/span><\/span><\/span>, este<\/b><\/span><\/span><\/span>per\u00edodo tamb\u00e9m deve<\/b><\/span><\/span><\/span> <\/b>aumentar.<\/b><\/span><\/span><\/span><\/p>\n

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

10-<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

11- <\/b><\/span><\/span><\/span>Se uma <\/b><\/span><\/span><\/span>placa met\u00e1lica com orif\u00edcio for aquecida<\/b><\/span><\/span><\/span>, verifica-se que o <\/b><\/span><\/span><\/span>orif\u00edcio aumenta<\/b><\/span><\/span><\/span>, como se<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

fosse <\/b><\/span><\/span><\/span>constitu\u00eddo pelo material da placa<\/b><\/span><\/span><\/span>, pois tudo se passa como se o <\/b><\/span><\/span><\/span>furo tivesse um coeficiente de dilata\u00e7\u00e3o superficial igual \u00e0quele da subst\u00e2ncia da placa.\u00a0<\/b><\/span><\/span><\/span><\/p>\n

Como o exerc\u00edcio se <\/b><\/span><\/span><\/span>refere aos raios voc\u00ea pode trabalhar com a <\/b><\/span><\/span><\/span>dilata\u00e7\u00e3o linear.<\/b><\/span><\/span><\/span><\/p>\n

Dilata\u00e7\u00e3o do <\/b><\/span><\/span><\/span>raio externo <\/b><\/span><\/span><\/span>R<\/b><\/span><\/span><\/span> para a arruela de <\/b><\/span><\/span><\/span>coeficiente de dilata\u00e7\u00e3o <\/b><\/span><\/span><\/span>\u03b1<\/b><\/span><\/span><\/span> para a <\/b><\/span><\/span><\/span>varia\u00e7\u00e3o de temperatura <\/b><\/span><\/span><\/span>\u0394\u03b8 — \u0394R = R.\u03b1.\u0394\u03b8 (I)<\/b><\/span><\/span><\/span><\/p>\n

Dilata\u00e7\u00e3o do <\/b><\/span><\/span><\/span>raio interno <\/b><\/span><\/span><\/span>r <\/b><\/span><\/span><\/span>para a arruela de <\/b><\/span><\/span><\/span>coeficiente de dilata\u00e7\u00e3o <\/b><\/span><\/span><\/span>\u03b1 <\/b><\/span><\/span><\/span>para a <\/b><\/span><\/span><\/span>varia\u00e7\u00e3o de temperatura<\/b><\/span><\/span><\/span><\/p>\n

\u0394\u03b8 — \u0394r = r.\u03b1.\u0394\u03b8 (II)<\/b><\/span><\/span><\/span><\/p>\n

(II)\/(I) — <\/b><\/span><\/span><\/span><\/b>\u0394r\/\u0394R = r.\u03b1.\u0394\u03b8\/ R.\u03b1.\u0394\u03b8 <\/b><\/span><\/span><\/span>— <\/b><\/span><\/span><\/span>\u0394r = (r\/R).\u0394R.<\/b><\/span><\/span><\/span><\/p>\n

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

12- <\/b><\/span><\/span><\/span>Resson\u00e2ncia<\/b><\/span><\/span><\/span><\/p>\n

Qualquer <\/b><\/span><\/span><\/span>sistema f\u00edsico possui uma ou mais freq\u00fc\u00eancias naturais de vibra\u00e7\u00e3o<\/b><\/span><\/span><\/span>. Quando ele \u00e9 <\/b><\/span><\/span><\/span>\u201cexcitado\u201d por algum agente externo, agindo no ritmo de uma dessas freq\u00fc\u00eancias<\/b><\/span><\/span><\/span>, surge o fen\u00f4meno da <\/b><\/span><\/span><\/span>resson\u00e2ncia<\/b><\/span><\/span><\/span>, ou seja, ele come\u00e7a a <\/b><\/span><\/span><\/span>oscilar gradativamente at\u00e9 atingir uma dessas freq\u00fc\u00eancias, onde sua amplitude \u00e9 m\u00e1xima.<\/b><\/span><\/span><\/span><\/p>\n

Exemplos:<\/b><\/span><\/span><\/span><\/p>\n

– <\/b><\/span><\/span><\/span>Uma crian\u00e7a, <\/b><\/span><\/span><\/span>num balan\u00e7o<\/b><\/span><\/span><\/span> j\u00e1 em movimento, sabe qual \u00e9 o momento certo, para que, com o<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

movimento do corpo provoque\u00a0um impulso, que faz aumentar a amplitude do movimento, obtendo assim, a resson\u00e2ncia. Trata-se de <\/b><\/span><\/span><\/span>resson\u00e2ncia mec\u00e2nica.<\/b><\/span><\/span><\/span><\/p>\n

– <\/b><\/span><\/span><\/span>Ao sintonizar uma <\/b><\/span><\/span><\/span>emissora de r\u00e1dio ou TV<\/b><\/span><\/span><\/span> estamos fazendo com que nosso <\/b><\/span><\/span><\/span>aparelho receptor<\/b><\/span><\/span><\/span> entre em <\/b><\/span><\/span><\/span>resson\u00e2ncia com a mesma freq\u00fc\u00eancia que a das ondas eletromagn\u00e9ticas da esta\u00e7\u00e3o que as emitiu. Trata-se de <\/b><\/span><\/span><\/span>resson\u00e2ncia eletr\u00f4nica.<\/b><\/span><\/span><\/span><\/p>\n

–<\/b><\/span><\/span><\/span> As <\/b><\/span><\/span><\/span>vibra\u00e7\u00f5es da corda de um viol\u00e3o entram em resson\u00e2ncia <\/b><\/span><\/span><\/span>com o ar contido em sua\u00a0 caixa de<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

madeira \u201ccaixa de resson\u00e2ncia\u201d ou com o a <\/b><\/span><\/span><\/span>nota emitida por um diapas\u00e3o<\/b><\/span><\/span><\/span>, que vibram com a <\/b><\/span><\/span><\/span>mesma freq\u00fc\u00eanci<\/b><\/span><\/span><\/span>a da nota emitida pelo diapas\u00e3o, afinando a corda do mesmo. Trata-se de <\/b><\/span><\/span><\/span>resson\u00e2ncia sonora.<\/b><\/span><\/span><\/span><\/p>\n

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

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

A <\/b><\/span><\/span><\/span>rela\u00e7\u00e3o entre o 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, ou seja,\u00a0 seni\/senr=n<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span>\/n<\/b><\/span><\/span><\/span>1\u00a0\u00a0\u00a0<\/b><\/span><\/span><\/sub><\/span><\/p>\n

\"\"<\/p>\n

\"\"<\/p>\n

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

\"\"<\/p>\n

Pelo <\/b><\/span><\/span><\/span>princ\u00edpio da reversibilidade<\/b><\/span><\/span><\/span> (caminho inverso), quando a luz <\/b><\/span><\/span><\/span>passa de um meio mais refringente (maior \u00edndice de refra\u00e7\u00e3o) para um menos refringente (menor \u00edndice de refra\u00e7\u00e3o) <\/b><\/span><\/span><\/span>\u00e2ngulo de refra\u00e7\u00e3o<\/b><\/span><\/span><\/span><\/span> <\/b>ser\u00e1 maior que o \u00e2ngulo de incid\u00eancia.<\/b><\/span><\/span><\/span><\/span><\/b><\/p>\n

Como o enunciado quer o <\/b><\/span><\/span><\/span>maior \u00e2ngulo de refra\u00e7\u00e3o,<\/b><\/span><\/span><\/span> o raio de luz <\/b><\/span><\/span><\/span>deve passar<\/b><\/span><\/span><\/span> do meio de <\/b><\/span><\/span><\/span>maior \u00edndice do l\u00edquido (benzeno 1,50) para o meio de menor \u00edndice do vidro (crown 1,52).<\/b><\/span><\/span><\/span><\/p>\n

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

14- <\/b><\/span><\/span><\/span>Trabalho da for\u00e7a el\u00e9trica<\/b><\/span><\/span><\/span> para levar o el\u00e9tron de <\/b><\/span><\/span><\/span>carga q=1,6.10<\/b><\/span><\/span><\/span>-19<\/b><\/span><\/span><\/sup><\/span>C<\/b><\/span><\/span><\/span>, da placa aceleradora A de<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

potencial V<\/b><\/span><\/span><\/span>A<\/b><\/span><\/span><\/sub><\/span> at\u00e9 a B, de potencial V<\/b><\/span><\/span><\/span>B<\/b><\/span><\/span><\/sub><\/span>, cuja diferen\u00e7a de potencial \u00e9 <\/b><\/span><\/span><\/span>U<\/b><\/span><\/span><\/span>AB<\/b><\/span><\/span><\/sub><\/span> <\/b>— <\/b><\/span><\/span><\/span>W<\/b><\/span><\/span><\/span>AB<\/b><\/span><\/span><\/sub><\/span> = q.U<\/b><\/span><\/span><\/span>AB<\/b><\/span><\/span><\/sub><\/span> —<\/b><\/span><\/span><\/span><\/p>\n

W<\/b><\/span><\/span><\/span>AB<\/b><\/span><\/span><\/sub><\/span>= 1,6.10<\/b><\/span><\/span><\/span>-19<\/b><\/span><\/span><\/sup><\/span>.U<\/b><\/span><\/span><\/span>AB<\/b><\/span><\/span><\/sub><\/span> (I).<\/b><\/span><\/span><\/span><\/p>\n

Utilizando o <\/b><\/span><\/span><\/span>teorema da varia\u00e7\u00e3o da energia cin\u00e9tica entre as placas A e B<\/b><\/span><\/span><\/span> onde, a velocidade do<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

el\u00e9tron de <\/b><\/span><\/span><\/span>massa m = 9,1.10<\/b><\/span><\/span><\/span>-31<\/b><\/span><\/span><\/sup><\/span>kg<\/b><\/span><\/span><\/span> em A \u00e9 nula (velocidade desprez\u00edvel <\/b><\/span><\/span><\/span>v<\/b><\/span><\/span><\/span>A<\/b><\/span><\/span><\/sub><\/span>=0)<\/b><\/span><\/span><\/span> e em B \u00e9 <\/b><\/span><\/span><\/span>v<\/b><\/span><\/span><\/span>B <\/b><\/span><\/span><\/sub><\/span>= 4.10<\/b><\/span><\/span><\/span>7<\/b><\/span><\/span><\/sup><\/span>m\/s.<\/b><\/span><\/span><\/span><\/p>\n

W<\/b><\/span><\/span><\/span>AB<\/b><\/span><\/span><\/sub><\/span> = E<\/b><\/span><\/span><\/span>cB<\/b><\/span><\/span><\/sub><\/span> \u2013 E<\/b><\/span><\/span><\/span>cA<\/b><\/span><\/span><\/sub><\/span> = <\/b><\/span><\/span><\/span>mv<\/b><\/span><\/span><\/span>B<\/b><\/span><\/span><\/sub><\/span>2 <\/b><\/span><\/span><\/sup><\/span>\/2<\/b><\/span><\/span><\/span> <\/b>\u2013 mv<\/b><\/span><\/span><\/span>A<\/b><\/span><\/span><\/sub><\/span>2<\/b><\/span><\/span><\/sup><\/span>\/2<\/b><\/span><\/span><\/span> = 9,1.10<\/b><\/span><\/span><\/span>-31<\/b><\/span><\/span><\/sup><\/span>.(4.10<\/b><\/span><\/span><\/span>7<\/b><\/span><\/span><\/sup><\/span>)<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sup><\/span>\/2 \u2013 9,1.10<\/b><\/span><\/span><\/span>-31<\/b><\/span><\/span><\/sup><\/span>.0<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sup><\/span>\/2 = 9,1.10<\/b><\/span><\/span><\/span>-31<\/b><\/span><\/span><\/sup><\/span>.16.10<\/b><\/span><\/span><\/span>14<\/b><\/span><\/span><\/sup><\/span>\/2 \u2013 0 —<\/b><\/span><\/span><\/span><\/p>\n

W<\/b><\/span><\/span><\/span>AB<\/b><\/span><\/span><\/sub><\/span> = 145,6.10<\/b><\/span><\/span><\/span>-17<\/b><\/span><\/span><\/sup><\/span>\/2 — <\/b><\/span><\/span><\/span>W<\/b><\/span><\/span><\/span>AB<\/b><\/span><\/span><\/sub><\/span> = 72,8.10<\/b><\/span><\/span><\/span>-17<\/b><\/span><\/span><\/sup><\/span> J (II).<\/b><\/span><\/span><\/span><\/p>\n

(I) em (II)<\/b><\/span><\/span><\/span> — 1,6.10<\/b><\/span><\/span><\/span>-19<\/b><\/span><\/span><\/sup><\/span>U<\/b><\/span><\/span><\/span>AB<\/b><\/span><\/span><\/sub><\/span> = 72,8.10<\/b><\/span><\/span><\/span>-17<\/b><\/span><\/span><\/sup><\/span> — <\/b><\/span><\/span><\/span>U<\/b><\/span><\/span><\/span>AB<\/b><\/span><\/span><\/sub><\/span> <\/b>= 45,5.10<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sup><\/span> <\/b>= 4,55.10<\/b><\/span><\/span><\/span>3 <\/b><\/span><\/span><\/sup><\/span>V<\/b><\/span><\/span><\/span>.<\/b><\/span><\/span><\/span><\/p>\n

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

15- <\/b><\/span><\/span><\/span>Quando um <\/b><\/span><\/span><\/span>solen\u00f3ide \u00e9 percorrido por corrente el\u00e9trica<\/b><\/span><\/span><\/span>, a configura\u00e7\u00e3o de suas linhas de indu\u00e7\u00e3o \u00e9 obtida pela reuni\u00e3o das <\/b><\/span><\/span><\/span>configura\u00e7\u00f5es de cada espira<\/b><\/span><\/span><\/span> o que equivale \u00e0 <\/b><\/span><\/span><\/span>configura\u00e7\u00e3o das linhas de indu\u00e7\u00e3o de um im\u00e3 natural.<\/b><\/span><\/span><\/span><\/p>\n

O <\/b><\/span><\/span><\/span>sentido<\/b><\/span><\/span><\/span> das linhas de indu\u00e7\u00e3o no solen\u00f3ide \u00e9 fornecido pela <\/b><\/span><\/span><\/span>regra da m\u00e3o direita<\/b><\/span><\/span><\/span> aplicada em uma<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

de suas espiras <\/b><\/span><\/span><\/span>(figura 2)<\/b><\/span><\/span><\/span> e em seu interior o campo magn\u00e9tico \u00e9 praticamente uniforme <\/b><\/span><\/span><\/span>(figura 1) e fora s\u00e3o linhas que saem do p\u00f3lo norte e chegam ao p\u00f3lo sul.<\/b><\/span><\/span><\/span><\/p>\n

\"\"\u00a0As linhas <\/b><\/span><\/span><\/span>de for\u00e7a do campo magn\u00e9tico produzido por um solen\u00f3ide s\u00e3o id\u00eanticas aos do campo magn\u00e9tico produzido por um im\u00e3.<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

Na pr\u00e1tica, \u00e9 <\/b><\/span><\/span><\/span>indiferente<\/b><\/span><\/span><\/span> produzir-se um campo magn\u00e9tico por um \u00edm\u00e3 ou por um solen\u00f3ide.<\/b><\/span><\/span><\/span><\/p>\n

Observe <\/b><\/span><\/span><\/span>nas figuras abaixo<\/b><\/span><\/span><\/span> que, como a corrente el\u00e9trica sai do <\/b><\/span><\/span><\/span>polo positivo da bateria<\/b><\/span><\/span><\/span>, utilizando<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

a regra da <\/b><\/span><\/span><\/span>m\u00e3o direita, os p\u00f3los do im\u00e3 ter\u00e3o a distribui\u00e7\u00e3o da figura da direita.<\/b><\/span><\/span><\/span><\/p>\n

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

 <\/p>\n

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

RESOLU\u00c7\u00d5ES 01- 02-) a) Observe na figura abaixo que, depois que o objeto foi preso \u00e0 mola que estava em seu comprimento natural de 20cm, ela foi deformada com seucomprimento passando para 25cm e sofrendo uma deforma\u00e7\u00e3o de \u2206x = 5cm = 0,05m, quando atingiu a situa\u00e7\u00e3o de equil\u00edbrio. Na situa\u00e7\u00e3o de equil\u00edbrio, as for\u00e7as que agem sobre o objeto<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":372,"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-374","page","type-page","status-publish","hentry"],"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/pages\/374","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=374"}],"version-history":[{"count":2,"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/pages\/374\/revisions"}],"predecessor-version":[{"id":378,"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/pages\/374\/revisions\/378"}],"up":[{"embeddable":true,"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/pages\/372"}],"wp:attachment":[{"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/media?parent=374"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}