{"id":2732,"date":"2017-02-07T04:01:30","date_gmt":"2017-02-07T04:01:30","guid":{"rendered":"http:\/\/fisicaevestibular.com.br\/novo\/?page_id=2732"},"modified":"2024-09-03T14:43:46","modified_gmt":"2024-09-03T14:43:46","slug":"puc-sp-2017-resolucao","status":"publish","type":"page","link":"https:\/\/fisicaevestibular.com.br\/novo\/universidades-2017\/puc-sp-2017\/puc-sp-2017-resolucao\/","title":{"rendered":"PUC-SP \u2013 2017 – Resolu\u00e7\u00e3o"},"content":{"rendered":"

Resolu\u00e7\u00e3o comentada das quest\u00f5es de F\u00edsica do vestibular da <\/span><\/span><\/span><\/p>\n

PUC-SP \u2013 017<\/span><\/span><\/span><\/p>\n

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

Rendimento real \u03b7 do motor<\/b><\/span><\/span><\/span><\/p>\n

A <\/b><\/span><\/span><\/span>pot\u00eancia total <\/b><\/span><\/span><\/span>absorvida por esse motor em <\/b><\/span><\/span><\/span>\u2206t = 1 s <\/b><\/span><\/span><\/span>vale <\/b><\/span><\/span><\/span>P<\/b><\/span><\/span><\/span>t<\/b><\/span><\/span><\/sub><\/span> = \"\"<\/b><\/span><\/span><\/span> <\/b>=<\/b><\/span><\/span><\/span> \"\"<\/b><\/span><\/span><\/span> <\/b>=<\/b><\/span><\/span><\/span> \"\"<\/b><\/span><\/span><\/span> <\/b><\/p>\n

P<\/b><\/span><\/span><\/span>t<\/b><\/span><\/span><\/sub><\/span> = 3700 J\/s \"\"<\/b><\/span><\/span><\/span> <\/b> <\/b>P<\/b><\/span><\/span><\/span>t<\/b><\/span><\/span><\/sub><\/span> = 3700 W. <\/b><\/span><\/span><\/span><\/p>\n

Pot\u00eancia \u00fatil <\/b><\/span><\/span><\/span>do motor \"\" P<\/b><\/span><\/span><\/span>u<\/b><\/span><\/span><\/sub><\/span> = 2,5×740 \"\" <\/b><\/span><\/span><\/span>P<\/b><\/span><\/span><\/span>u<\/b><\/span><\/span><\/sub><\/span> = 1850 W.<\/b><\/span><\/span><\/span><\/p>\n

Rendimento do motor \"\" \u03b7<\/b><\/span><\/span><\/span>m<\/b><\/span><\/span><\/sub><\/span> <\/b>=P<\/b><\/span><\/span><\/span>u<\/b><\/span><\/span><\/sub><\/span>\/P<\/b><\/span><\/span><\/span>t<\/b><\/span><\/span><\/sub><\/span> <\/b>=<\/b><\/span><\/span><\/span> \"\"<\/b><\/span><\/span><\/span> \"\" <\/b><\/span><\/span><\/span>\u03b7<\/b><\/span><\/span><\/span>m<\/b><\/span><\/span><\/sub><\/span> =<\/b><\/span><\/span><\/span> 0,5 (50%)<\/b><\/span><\/span><\/span> <\/b><\/p>\n

Rendimento de um motor de Carnot<\/b><\/span><\/span><\/span><\/p>\n

Temperatura T<\/b><\/span><\/span><\/span>f<\/b><\/span><\/span><\/sub><\/span> da fonte fria \"\" T<\/b><\/span><\/span><\/span>f<\/b><\/span><\/span><\/sub><\/span> =927 +273 <\/b><\/span><\/span><\/span>= 1200 K.<\/b><\/span><\/span><\/span><\/p>\n

Temperatura T<\/b><\/span><\/span><\/span>Q<\/b><\/span><\/span><\/sub><\/span> da fonte quente \"\" \"\"<\/b><\/span><\/span><\/span> <\/b>=<\/b><\/span><\/span><\/span> \"\"<\/b><\/span><\/span><\/span> \"\" \"\"<\/b><\/span><\/span><\/span> <\/b>=<\/b><\/span><\/span><\/span> \"\" \"\" \"\" <\/b><\/span><\/span><\/span>=<\/b><\/span><\/span><\/span> \"\"<\/b><\/span><\/span><\/span> \"\" <\/b><\/span><\/span><\/span>403 \u2013 160 = 9C \"\" <\/b><\/span><\/span><\/span>C = 27 <\/b><\/span><\/span><\/span>o<\/b><\/span><\/span><\/sup><\/span>C \"\" T<\/b><\/span><\/span><\/span>Q<\/b><\/span><\/span><\/sub><\/span> = <\/b><\/span><\/span><\/span>27+273 <\/b><\/span><\/span><\/span>= 300 K.<\/b><\/span><\/span><\/span><\/p>\n

O rendimento <\/b><\/span><\/span><\/span>\u03b7<\/b><\/span><\/span><\/span>C<\/b><\/span><\/span><\/sub><\/span> de um motor de Carnot <\/b><\/span><\/span><\/span>operando entre as temperaturas acima <\/b><\/span><\/span><\/span>\u00e9 fornecido pela express\u00e3o \"\" \u03b7<\/b><\/span><\/span><\/span>C<\/b><\/span><\/span><\/sub><\/span> = 1 \u2013 T<\/b><\/span><\/span><\/span>Q<\/b><\/span><\/span><\/sub><\/span>\/T<\/b><\/span><\/span><\/span>f<\/b><\/span><\/span><\/sub><\/span> = <\/b><\/span><\/span><\/span>1 – \"\"<\/b><\/span><\/span><\/span> <\/b>= 1 \u2013 0,25<\/b><\/span><\/span><\/span> \"\"<\/b><\/span><\/span><\/span> <\/b>\u03b7<\/b><\/span><\/span><\/span>C<\/b><\/span><\/span><\/sub><\/span> = 0,75 (75%)<\/b><\/span><\/span><\/span><\/p>\n

Raz\u00e3o pedida<\/b><\/span><\/span><\/span> \"\" <\/b><\/span><\/span><\/span>\u03b7<\/b><\/span><\/span><\/span>C<\/b><\/span><\/span><\/sub><\/span>\/\u03b7<\/b><\/span><\/span><\/span>m<\/b><\/span><\/span><\/sub><\/span> = \"\"<\/b><\/span><\/span><\/span> \"\" <\/b><\/span><\/span><\/span>\u03b7<\/b><\/span><\/span><\/span>C<\/b><\/span><\/span><\/sub><\/span>\/\u03b7<\/b><\/span><\/span><\/span>m<\/b><\/span><\/span><\/sub><\/span> = 1,5<\/b><\/span><\/span><\/span><\/p>\n

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

02- <\/span><\/span><\/span>As <\/b><\/span><\/span><\/span>for\u00e7as trocadas <\/b><\/span><\/span><\/span>entre o <\/b><\/span><\/span><\/span>trem e a camionete <\/b><\/span><\/span><\/span>obedecem ao <\/b><\/span><\/span><\/span>princ\u00edpio da a\u00e7\u00e3o e rea\u00e7\u00e3o<\/b><\/span><\/span><\/span>, ou seja, tem sempre a <\/b><\/span><\/span><\/span>mesma intensidade, mesma dire\u00e7\u00e3o, mas sentidos contr\u00e1rios.<\/b><\/span><\/span><\/span><\/p>\n

Choque inel\u00e1stico<\/b><\/span><\/span><\/span><\/span><\/p>\n

Neste tipo de choque a<\/b><\/span><\/span>\u00a0<\/b><\/span><\/span>dissipa\u00e7\u00e3o de energia \u00e9 m\u00e1xima,<\/b><\/span><\/span>\u00a0<\/b><\/span><\/span>o<\/b><\/span><\/span>\u00a0<\/b><\/span><\/span>coeficiente de restitui\u00e7\u00e3o \u00e9 nulo<\/b><\/span><\/span>, e,<\/b><\/span><\/span>\u00a0<\/b><\/span><\/span>ap\u00f3s<\/b><\/span><\/span>\u00a0<\/b><\/span><\/span>o choque, os<\/b><\/span><\/span>\u00a0<\/b><\/span><\/span>corpos obrigatoriamente se juntam e se movem unidos com a mesma velocidade.<\/b><\/span><\/span>\u00a0<\/b><\/span><\/span>Lembre-se de que em<\/b><\/span><\/span>\u00a0<\/b><\/span><\/span>qualquer tipo<\/b><\/span><\/span>\u00a0<\/b><\/span><\/span>de choque a<\/b><\/span><\/span>\u00a0<\/b><\/span><\/span>quantidade de movimento sempre se conserva<\/b><\/span><\/span>.<\/b><\/span><\/span><\/span><\/span><\/p>\n

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

03- <\/span><\/span><\/span>Se voc\u00ea n\u00e3o domina a teoria, ela est\u00e1 a seguir:<\/b><\/span><\/span><\/span><\/p>\n

Cor de um corpo<\/b><\/span><\/span><\/span><\/span><\/p>\n

\u00a0A<\/b><\/span><\/span>\u00a0<\/b><\/span><\/span>luz branca do Sol ou de uma l\u00e2mpada<\/b><\/span><\/span>\u00a0<\/b><\/span><\/span>qualquer \u00e9 denominada<\/b><\/span><\/span>\u00a0<\/b><\/span><\/span>luz policrom\u00e1tica (v\u00e1rias cores)<\/b><\/span><\/span>\u00a0<\/b><\/span><\/span>e \u00e9 composta das<\/b><\/span><\/span>\u00a0<\/b><\/span><\/span>cores monocrom\u00e1ticas (uma s\u00f3 cor), vermelho, alaranjado, amarelo, verde, azul, anil e violeta.<\/b><\/span><\/span><\/span><\/span><\/p>\n

A<\/b><\/span><\/span>\u00a0<\/b><\/span><\/span>cor apresentada por um corpo,<\/b><\/span><\/span>\u00a0<\/b><\/span><\/span>ao ser iluminado,<\/b><\/span><\/span>\u00a0<\/b><\/span><\/span>depende do tipo de luz que ele reflete difusamente<\/b><\/span><\/span>\u00a0<\/b><\/span><\/span>(espalha em todas as dire\u00e7\u00f5es e sentidos) e<\/b><\/span><\/span>\u00a0<\/b><\/span><\/span>que chega aos olhos do observador.<\/b><\/span><\/span><\/span><\/span><\/p>\n

Um<\/b><\/span><\/span>\u00a0<\/b><\/span><\/span>corpo negro absorve todas as cores<\/b><\/span><\/span>\u00a0<\/b><\/span><\/span>e um<\/b><\/span><\/span>\u00a0<\/b><\/span><\/span>corpo branco reflete todas as cores.<\/b><\/span><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

\u00a0Figura 1<\/b><\/span><\/span>\u00a0\"\"<\/b><\/span><\/span>\u00a0<\/b><\/span><\/span>O<\/b><\/span><\/span>\u00a0<\/b><\/span><\/span>corpo vermelho<\/b><\/span><\/span>\u00a0<\/b><\/span><\/span>reflete difusamente<\/b><\/span><\/span>\u00a0<\/b><\/span><\/span>apenas a cor vermelha<\/b><\/span><\/span>\u00a0<\/b><\/span><\/span>e o<\/b><\/span><\/span>\u00a0<\/b><\/span><\/span>observador enxergar\u00e1 vermelho.<\/b><\/span><\/span><\/span><\/span><\/p>\n

Figura 2<\/b><\/span><\/span>\u00a0\"\"<\/b><\/span><\/span>\u00a0<\/b><\/span><\/span>As<\/b><\/span><\/span>\u00a0<\/b><\/span><\/span>sete cores (policrom\u00e1tica branca)<\/b><\/span><\/span>\u00a0<\/b><\/span><\/span>incidem<\/b><\/span><\/span>\u00a0<\/b><\/span><\/span>sobre o<\/b><\/span><\/span>\u00a0<\/b><\/span><\/span>corpo amarelo que reflete difusamente somente o amarelo<\/b><\/span><\/span>\u00a0<\/b><\/span><\/span>e o<\/b><\/span><\/span>\u00a0<\/b><\/span><\/span>observador enxergar\u00e1 essa cor.<\/b><\/span><\/span><\/span><\/span><\/p>\n

Figura 3<\/b><\/span><\/span>\u00a0\"\"<\/b><\/span><\/span>\u00a0 As<\/b><\/span><\/span>\u00a0<\/b><\/span><\/span>sete cores (policrom\u00e1tica branca) incidem<\/b><\/span><\/span>\u00a0<\/b><\/span><\/span>sobre o<\/b><\/span><\/span>\u00a0<\/b><\/span><\/span>corpo verde que reflete difusamente somente o verde<\/b><\/span><\/span>\u00a0<\/b><\/span><\/span>e o observador<\/b><\/span><\/span>\u00a0<\/b><\/span><\/span>enxergar\u00e1 verde.<\/b><\/span><\/span><\/span><\/span><\/p>\n

Figura 4<\/b><\/span><\/span>\u00a0\"\"\u00a0<\/b><\/span><\/span>O corpo negro absorve todas as cores<\/b><\/span><\/span>\u00a0<\/b><\/span><\/span>e<\/b><\/span><\/span>\u00a0<\/b><\/span><\/span>nenhuma chegar\u00e1 ao observador<\/b><\/span><\/span>\u00a0<\/b><\/span><\/span>que<\/b><\/span><\/span>ver\u00e1 negro (aus\u00eancia de cores).<\/b><\/span><\/span><\/span><\/span><\/p>\n

Figura 5<\/b><\/span><\/span>\u00a0\"\"<\/b><\/span><\/span>\u00a0<\/b><\/span><\/span>O<\/b><\/span><\/span>\u00a0<\/b><\/span><\/span>corpo violeta reflete difusamente somente o violeta<\/b><\/span><\/span>\u00a0<\/b><\/span><\/span>e<\/b><\/span><\/span>\u00a0<\/b><\/span><\/span>absorver\u00e1 o verde,<\/b><\/span><\/span>\u00a0<\/b><\/span><\/span>n\u00e3o<\/b><\/span><\/span>chegando nenhuma luz ao observador, que ver\u00e1 negro.<\/b><\/span><\/span><\/span><\/span><\/p>\n

Figura 6<\/b><\/span><\/span>\u00a0\"\"<\/b><\/span><\/span>\u00a0<\/b><\/span><\/span>O<\/b><\/span><\/span>\u00a0<\/b><\/span><\/span>observador ver\u00e1 vermelho<\/b><\/span><\/span>, pois o<\/b><\/span><\/span>\u00a0<\/b><\/span><\/span>corpo branco reflete difusamente todas as cores inclusive o vermelho.<\/b><\/span><\/span><\/span><\/span><\/p>\n

No <\/b><\/span><\/span><\/span>caso do exerc\u00edcio<\/b><\/span><\/span><\/span>, as <\/b><\/span><\/span><\/span>palavras <\/b><\/span><\/span><\/span>que voc\u00ea enxergar\u00e1 <\/b><\/span><\/span><\/span>em azul <\/b><\/span><\/span><\/span>s\u00e3o <\/b><\/span><\/span><\/span>PRETO, VERDE e VERMELHO <\/b><\/span><\/span><\/span>e as cores ser\u00e3o <\/b><\/span><\/span><\/span>azul <\/b><\/span><\/span><\/span>(as tr\u00eas palavras anteriores) e <\/b><\/span><\/span><\/span>preta<\/b><\/span><\/span><\/span> (as <\/b><\/span><\/span><\/span>demais radia\u00e7\u00f5es <\/b><\/span><\/span><\/span>ser\u00e3o absorvidas fornecendo a <\/b><\/span><\/span><\/span>sensa\u00e7\u00e3o visual de preto<\/b><\/span><\/span><\/span>).<\/b><\/span><\/span><\/span><\/p>\n

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

04- <\/span><\/span><\/span>Vamos <\/b><\/span><\/span><\/span>chamar<\/b><\/span><\/span><\/span> de <\/b><\/span><\/span><\/span>d <\/b><\/span><\/span><\/span>a <\/b><\/span><\/span><\/span>primeira metade do trajeto,<\/b><\/span><\/span><\/span> tal que:<\/b><\/span><\/span><\/span><\/p>\n

\"\" Quando percorrida com V<\/b><\/span><\/span><\/span>1<\/b><\/span><\/span><\/sub><\/span> = 25 m\/s <\/b><\/span><\/span><\/span>demora um <\/b><\/span><\/span><\/span>intervalo de tempo \u2206t<\/b><\/span><\/span><\/span>1<\/b><\/span><\/span><\/sub><\/span> <\/b>tal que <\/b><\/span><\/span><\/span>V<\/b><\/span><\/span><\/span>1<\/b><\/span><\/span><\/sub><\/span> = d\/\u2206t<\/b><\/span><\/span><\/span>1<\/b><\/span><\/span><\/sub><\/span> \"\" <\/b><\/span><\/span><\/span>25 = d\/\u2206t<\/b><\/span><\/span><\/span>1<\/b><\/span><\/span><\/sub><\/span> \"\" <\/b><\/span><\/span><\/span>\u2206t<\/b><\/span><\/span><\/span>1<\/b><\/span><\/span><\/sub><\/span> = \"\" (I) <\/b><\/span><\/span><\/span><\/p>\n

\"\" Quando percorrida com V<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span> = 15 m\/s <\/b><\/span><\/span><\/span>demora um <\/b><\/span><\/span><\/span>intervalo de tempo \u2206t<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span> = \u2206t<\/b><\/span><\/span><\/span>1<\/b><\/span><\/span><\/sub><\/span> + 7200 <\/b><\/span><\/span><\/span>tal que <\/b><\/span><\/span><\/span>V<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span> = d\/\u2206t<\/b><\/span><\/span><\/span>2 <\/b><\/span><\/span><\/sub><\/span> \"\" 15 = d\/(\u2206t<\/b><\/span><\/span><\/span>1<\/b><\/span><\/span><\/sub><\/span> + 7200) (II).<\/b><\/span><\/span><\/span><\/p>\n

(I) em (II) \"\" <\/b><\/span><\/span><\/span>15 = d\/(\"\" + 7200) \"\" 15.\"\" + 15.7200 = d \"\" 0,6d \u2013 d = – 108000 \"\" 0,4d = 108000 \"\" <\/b><\/span><\/span><\/span>d = 270 000 m = 270 km (III).<\/b><\/span><\/span><\/span><\/p>\n

(III) em (I) \"\" \u2206t<\/b><\/span><\/span><\/span>1<\/b><\/span><\/span><\/sub><\/span> <\/b>= \"\"<\/b><\/span><\/span><\/span> <\/b>= 10800 s<\/b><\/span><\/span><\/span> \"\"<\/b><\/span><\/span><\/span> <\/b>\u2206t<\/b><\/span><\/span><\/span>1<\/b><\/span><\/span><\/sub><\/span> = \"\"<\/b><\/span><\/span><\/span> <\/b>= 3 <\/b><\/span><\/span><\/span>h \"\" <\/b><\/span><\/span><\/span>\u2206t<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span> = 3 + 2 \"\"<\/b><\/span><\/span><\/span> <\/b>\u2206t<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span> = 5 h (tempo gasto na primeira metade do trajeto com velocidade de 15 m\/s).<\/b><\/span><\/span><\/span><\/p>\n

Como a<\/b><\/span><\/span><\/span> primeira metade <\/b><\/span><\/span><\/span>do trajeto <\/b><\/span><\/span><\/span>tem 270 km, a <\/b><\/span><\/span><\/span>segunda metade ter\u00e1 <\/b><\/span><\/span><\/span>tamb\u00e9m 270 km e a <\/b><\/span><\/span><\/span>dist\u00e2ncia<\/b><\/span><\/span><\/span><\/p>\n

entre as duas cidades<\/b><\/span><\/span><\/span> ser\u00e1 de <\/b><\/span><\/span><\/span>D <\/b><\/span><\/span><\/span>= 270×2 <\/b><\/span><\/span><\/span>= 540 km<\/b><\/span><\/span><\/span>.<\/b><\/span><\/span><\/span><\/p>\n

Como, pelo <\/b><\/span><\/span><\/span>enunciado,<\/b><\/span><\/span><\/span> a <\/b><\/span><\/span><\/span>segunda metade V<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span> <\/b>desse trajeto \u00e9 sempre percorrida com <\/b><\/span><\/span><\/span>velocidade constante e igual \u00e0 m\u00e9dia aritm\u00e9tica das duas velocidades anteriore<\/b><\/span><\/span><\/span>s \"\" <\/b><\/span><\/span><\/span>V<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span> =<\/b><\/span><\/span><\/span> \"\" = 20 m\/sx3,6 <\/b><\/span><\/span><\/span>= 72 km\/h.<\/b><\/span><\/span><\/span><\/p>\n

Tempo \u2206t<\/b><\/span><\/span><\/span>3<\/b><\/span><\/span><\/sub><\/span> <\/b>decorrido para percorrer a <\/b><\/span><\/span><\/span>segunda metade do percurso de d = 270 km com V<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span> = 72 km\/h <\/b><\/span><\/span><\/span><\/p>\n

72 = 270\/\u2206t<\/b><\/span><\/span><\/span>3<\/b><\/span><\/span><\/sub><\/span> \"\" \u2206t<\/b><\/span><\/span><\/span>3<\/b><\/span><\/span><\/sub><\/span> = \"\"<\/b><\/span><\/span><\/span> <\/b>= 3,75 h <\/b><\/span><\/span><\/span><\/p>\n

A <\/b><\/span><\/span><\/span>velocidade m\u00e9dia (V<\/b><\/span><\/span><\/span>m<\/b><\/span><\/span><\/sub><\/span>) ao longo de todo o trajeto<\/b><\/span><\/span><\/span> <\/b>\u00e9 fornecida por \"\" V<\/b><\/span><\/span><\/span>m<\/b><\/span><\/span><\/sub><\/span> = \"\"<\/b><\/span><\/span><\/span> <\/b>=<\/b><\/span><\/span><\/span> \"\" = \"\" \"\" <\/b><\/span><\/span><\/span>V<\/b><\/span><\/span><\/span>m<\/b><\/span><\/span><\/sub><\/span> = 80 km\/h<\/b><\/span><\/span><\/span><\/p>\n

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

05- <\/span><\/span><\/span>Calculando a massa de le<\/b><\/span><\/span><\/span>ite \"\" <\/b><\/span><\/span><\/span>densidade do leite = \"\"<\/b><\/span><\/span><\/span> \"\" m<\/b><\/span><\/span><\/span>L<\/b><\/span><\/span><\/sub><\/span> = d<\/b><\/span><\/span><\/span>L<\/b><\/span><\/span><\/sub><\/span>.V<\/b><\/span><\/span><\/span>L<\/b><\/span><\/span><\/sub><\/span> \"\"<\/b><\/span><\/span><\/span> m<\/b><\/span><\/span><\/span>L<\/b><\/span><\/span><\/sub><\/span> = 1 (g\/mL).V<\/b><\/span><\/span><\/span>L<\/b><\/span><\/span><\/sub><\/span>(g) \"\" <\/b><\/span><\/span><\/span>m<\/b><\/span><\/span><\/span>L <\/b><\/span><\/span><\/sub><\/span>= V<\/b><\/span><\/span><\/span>L<\/b><\/span><\/span><\/sub><\/span> (g)<\/b><\/span><\/span><\/span><\/p>\n

Calculando a massa de caf\u00e9<\/b><\/span><\/span><\/span> \"\" <\/b><\/span><\/span><\/span>densidade do caf\u00e9 = \"\"<\/b><\/span><\/span><\/span> \"\" m<\/b><\/span><\/span><\/span>c<\/b><\/span><\/span><\/sub><\/span> = d<\/b><\/span><\/span><\/span>c<\/b><\/span><\/span><\/sub><\/span>.V<\/b><\/span><\/span><\/span>c<\/b><\/span><\/span><\/sub><\/span> \"\"<\/b><\/span><\/span><\/span> m<\/b><\/span><\/span><\/span>c<\/b><\/span><\/span><\/sub><\/span> = 1g\/mL.30 mL \"\" <\/b><\/span><\/span><\/span>m<\/b><\/span><\/span><\/span>c<\/b><\/span><\/span><\/sub><\/span> = 30 g <\/b><\/span><\/span><\/span><\/p>\n

Ap\u00f3s a mistura ambos<\/b><\/span><\/span><\/span> ter\u00e3o a <\/b><\/span><\/span><\/span>mesma temperatura <\/b><\/span><\/span><\/span>(de equil\u00edbrio t\u00e9rmico) \"\"<\/b><\/span><\/span><\/span> = 40 <\/b><\/span><\/span><\/span>o<\/b><\/span><\/span><\/sup><\/span>C.<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

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

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

For\u00e7a Magn\u00e9tica sobre um condutor retil\u00edneo imerso num campo magn\u00e9tico uniforme<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

\"\"<\/p>\n

\"\"<\/p>\n

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

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

A seguir, breve resumo te\u00f3rico:<\/b><\/span><\/span><\/span><\/p>\n

Transforma\u00e7\u00e3o isob\u00e1rica<\/b><\/span><\/span><\/span><\/p>\n

\u00a0<\/span>Ocorre \u00e0 press\u00e3o constante.<\/b><\/span><\/span><\/span>\u00a0A\u00a0<\/b><\/span><\/span><\/span>varia\u00e7\u00e3o de temperatura (\u0394T)<\/b><\/span><\/span><\/span> provoca uma <\/b><\/span><\/span><\/span>varia\u00e7\u00e3o de energia interna (\u0394U) do sistema <\/b><\/span><\/span><\/span>e a <\/b><\/span><\/span><\/span>varia\u00e7\u00e3o de volume (\u0394V) produz trabalho.<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

Parte\u00a0do calor (Q) recebido pelo sistema\u00a0<\/b><\/span><\/span><\/span>\u00e9\u00a0<\/b><\/span><\/span><\/span>armazenada sob forma de energia interna\u00a0<\/b><\/span><\/span><\/span>e <\/b><\/span><\/span><\/span>parte<\/b><\/span><\/span><\/span> \u00e9 <\/b><\/span><\/span><\/span>transformada em trabalho, <\/b><\/span><\/span><\/span>de modo que <\/b><\/span><\/span><\/span>\u0394U = Q \u2013 W.<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

No caso do exerc\u00edcio, s\u00e3o fornecidos:<\/b><\/span><\/span><\/span><\/p>\n

P = <\/b><\/span><\/span><\/span>constante = 1 atm <\/b><\/span><\/span><\/span>= 1.10<\/b><\/span><\/span><\/span>5<\/b><\/span><\/span><\/sup><\/span> N\/m<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sup><\/span> (Pa)<\/b><\/span><\/span><\/span><\/p>\n

Volume inicial \"\" V<\/b><\/span><\/span><\/span>o<\/b><\/span><\/span><\/sub><\/span> <\/b>= 1000 cm<\/b><\/span><\/span><\/span>3<\/b><\/span><\/span><\/sup><\/span> = 10<\/b><\/span><\/span><\/span>3<\/b><\/span><\/span><\/sup><\/span> cm<\/b><\/span><\/span><\/span>3<\/b><\/span><\/span><\/sup><\/span> = 10<\/b><\/span><\/span><\/span>3<\/b><\/span><\/span><\/sup><\/span>.(10<\/b><\/span><\/span><\/span>-6<\/b><\/span><\/span><\/sup><\/span> <\/b>m<\/b><\/span><\/span><\/span>3<\/b><\/span><\/span><\/sup><\/span>) \"\" <\/b><\/span><\/span><\/span>V<\/b><\/span><\/span><\/span>o<\/b><\/span><\/span><\/sub><\/span> = 10<\/b><\/span><\/span><\/span>-3<\/b><\/span><\/span><\/sup><\/span> m<\/b><\/span><\/span><\/span>3<\/b><\/span><\/span><\/sup><\/span><\/p>\n

Volume final que foi aumentado 300% \"\"<\/b><\/span><\/span><\/span> V =( \"\"<\/b><\/span><\/span><\/span> ).10<\/b><\/span><\/span><\/span>-3<\/b><\/span><\/span><\/sup><\/span> \"\" <\/b><\/span><\/span><\/span>V = 3.10<\/b><\/span><\/span><\/span>-3<\/b><\/span><\/span><\/sup><\/span> m<\/b><\/span><\/span><\/span>3<\/b><\/span><\/span><\/sup><\/span> <\/b><\/p>\n

C\u00e1lculo do<\/b><\/span><\/span><\/span> trabalho mec\u00e2nico, <\/b><\/span><\/span><\/span>em joules, <\/b><\/span><\/span><\/span>realizado pelo g\u00e1s durante <\/b><\/span><\/span><\/span>essa transforma\u00e7\u00e3o \"\" <\/b><\/span><\/span><\/span>W = P.\u2206V =<\/b><\/span><\/span><\/span> 10<\/b><\/span><\/span><\/span>5<\/b><\/span><\/span><\/sup><\/span>.(3.10<\/b><\/span><\/span><\/span>-3<\/b><\/span><\/span><\/sup><\/span> \u2013 1.10<\/b><\/span><\/span><\/span>-3<\/b><\/span><\/span><\/sup><\/span>) \"\" W = 10<\/b><\/span><\/span><\/span>5<\/b><\/span><\/span><\/sup><\/span>.2.10<\/b><\/span><\/span><\/span>-3<\/b><\/span><\/span><\/sup><\/span> \"\" W = 2.10<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sup><\/span> J<\/b><\/span><\/span><\/span><\/p>\n

Energia interna de um g\u00e1s perfeito<\/b><\/span><\/span><\/span><\/p>\n

A energia interna (U) de um <\/b><\/span><\/span><\/span>g\u00e1s perfeito monoat\u00f4mico\u00a0corresponde<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span>\u00e0 soma das energias cin\u00e9ticas m\u00e9dias (Ec) de todas as suas mol\u00e9culas e, pela lei de Joule \u00e9 fornecida por:<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

A energia interna de certa massa de um g\u00e1s perfeito \u00e9 fun\u00e7\u00e3o exclusiva da temperatura desse g\u00e1s<\/b><\/span><\/span><\/span><\/p>\n

Se U = (3\/2).n.R.T e PV = n.R.T \"\" U = (3\/2).PV \"\" \u2206U = (3\/2).P.\u2206V = <\/b><\/span><\/span><\/span>(\"\"<\/b><\/span><\/span><\/span> . 10<\/b><\/span><\/span><\/span>5<\/b><\/span><\/span><\/sup><\/span>.2.10<\/b><\/span><\/span><\/span>-3<\/b><\/span><\/span><\/sup><\/span> \"\"<\/b><\/span><\/span><\/span> \u2206U = 3.10<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sup><\/span> J. <\/b><\/span><\/span><\/span><\/p>\n

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

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

Velocidade de propaga\u00e7\u00e3o dos pulsos nos meios unidimensionais (corda)<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

\u00a0Considere um\u00a0<\/b><\/span><\/span><\/span>pulso ou v\u00e1rios pulsos sucessivos (onda)<\/b><\/span><\/span><\/span>se\u00a0<\/b><\/span><\/span><\/span>propagando<\/b><\/span><\/span><\/span>\u00a0com\u00a0<\/b><\/span><\/span><\/span>velocidade V\u00a0<\/b><\/span><\/span><\/span>numa<\/b><\/span><\/span><\/span><\/p>\n

corda tracionada\u00a0<\/b><\/span><\/span><\/span>(esticada) por uma\u00a0<\/b><\/span><\/span><\/span>for\u00e7a de intensidade F.<\/b><\/span><\/span><\/span><\/p>\n

Denominamos<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>densidade linear de massa (\u00b5)\u00a0<\/b><\/span><\/span><\/span>de uma\u00a0<\/b><\/span><\/span><\/span>corda homog\u00eanea,\u00a0<\/b><\/span><\/span><\/span>de\u00a0<\/b><\/span><\/span><\/span>se\u00e7\u00e3o transversal\u00a0 constante,\u00a0<\/b><\/span><\/span><\/span>que possui\u00a0<\/b><\/span><\/span><\/span>massa (m)\u00a0e\u00a0comprimento (L),\u00a0<\/b><\/span><\/span><\/span>\u00e0 express\u00e3o:<\/b><\/span><\/span><\/span><\/p>\n

Significado f\u00edsico de\u00a0\u00b5\u00a0\"\"<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>significa quanto\u00a0<\/b><\/span><\/span><\/span>de\u00a0<\/b><\/span><\/span><\/span>massa a corda tem por unidade de comprimento.<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span><\/p>\n

Assim, uma\u00a0<\/b><\/span><\/span><\/span>corda de 0,5 kg\/m\u00a0<\/b><\/span><\/span><\/span>possui, no SI,\u00a0<\/b><\/span><\/span><\/span>0,5kg de massa para cada 1 metro de comprimento.<\/b><\/span><\/span><\/span>\"\"<\/p>\n

A\u00a0<\/b><\/span><\/span><\/span>velocidade (V)\u00a0de propaga\u00e7\u00e3o do pulso na corda \u00e9 dada, <\/b><\/span><\/span><\/span>tamb\u00e9m<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>por:<\/b><\/span><\/span><\/span>\"\"<\/p>\n

Onde\u00a0<\/b><\/span><\/span><\/span>T \u00e9 a intensidade da for\u00e7a <\/b><\/span><\/span><\/span>que\u00a0<\/b><\/span><\/span><\/span>traciona\u00a0<\/b><\/span><\/span><\/span>(estica)\u00a0<\/b><\/span><\/span><\/span>a corda e \u00b5 \u00e9 a densidade linear de massa da mesma. (F\u00f3rmula de Taylor).<\/b><\/span><\/span><\/span><\/p>\n

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

\"\"<\/p>\n

Como a\u00a0<\/b><\/span><\/span><\/span>densidade linear\u00a0<\/b><\/span><\/span><\/span>da\u00a0<\/b><\/span><\/span><\/span>primeira corda (\u00b5<\/b><\/span><\/span><\/span>1<\/b><\/span><\/span><\/sub><\/span>)<\/b><\/span><\/span><\/span>\u00a0\u00e9\u00a0<\/b><\/span><\/span><\/span>maior do que a da segunda (\u00b5<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span>)<\/b><\/span><\/span><\/span>, ou seja,\u00a0<\/b><\/span><\/span><\/span>\u00b5<\/b><\/span><\/span><\/span>1<\/b><\/span><\/span><\/sub><\/span>\u00a0>\u00a0\u00b5<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span>,<\/b><\/span><\/span><\/span><\/p>\n

quando o\u00a0<\/b><\/span><\/span><\/span>pulso chega ao ponto de jun\u00e7\u00e3o das cordas,\u00a0<\/b><\/span><\/span><\/span>ocorre ao\u00a0<\/b><\/span><\/span><\/span>mesmo tempo refra\u00e7\u00e3o e reflex\u00e3o.<\/b><\/span><\/span><\/span> Esse ponto (jun\u00e7\u00e3o) funciona\u00a0<\/b><\/span><\/span><\/span>como uma\u00a0<\/b><\/span><\/span><\/span>extremidade livre\u00a0\u00a0e o\u00a0pulso refletido retorna sem invers\u00e3o de fase.<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

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

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

Medindo a altura em rela\u00e7\u00e3o ao ponto B (h),<\/b><\/span><\/span><\/span> sabendo que em <\/b><\/span><\/span><\/span>A, V<\/b><\/span><\/span><\/span>A<\/b><\/span><\/span><\/sub><\/span> = 0 <\/b><\/span><\/span><\/span>e, como os <\/b><\/span><\/span><\/span>atritos s\u00e3o desprezados, para calcular V<\/b><\/span><\/span><\/span>B<\/b><\/span><\/span><\/sub><\/span> voc\u00ea pode aplicar o princ\u00edpio da conserva\u00e7\u00e3o da energia mec\u00e2nica.<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

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

Observe atentamente o c\u00e1lculo do \u00e2ngulo<\/b><\/span><\/span><\/span> \"\"<\/b><\/span><\/span><\/span> pedido, fornecido abaixo:<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

Pela tabela fornecida \u03b1 = 48,6<\/b><\/span><\/span><\/span>o<\/b><\/span><\/span><\/sup><\/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\u00e7\u00e3o comentada das quest\u00f5es de F\u00edsica do vestibular da PUC-SP \u2013 017 01- Rendimento real \u03b7 do motor A pot\u00eancia total absorvida por esse motor em \u2206t = 1 s vale Pt = = = Pt = 3700 J\/s Pt = 3700 W. Pot\u00eancia \u00fatil do motor Pu = 2,5×740 Pu = 1850 W. Rendimento do motor \u03b7m =Pu\/Pt =<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":2730,"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-2732","page","type-page","status-publish","hentry"],"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/pages\/2732","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=2732"}],"version-history":[{"count":2,"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/pages\/2732\/revisions"}],"predecessor-version":[{"id":11050,"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/pages\/2732\/revisions\/11050"}],"up":[{"embeddable":true,"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/pages\/2730"}],"wp:attachment":[{"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/media?parent=2732"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}