{"id":2327,"date":"2016-07-09T23:54:52","date_gmt":"2016-07-09T23:54:52","guid":{"rendered":"http:\/\/fisicaevestibular.com.br\/novo\/?page_id=2327"},"modified":"2024-08-23T14:55:03","modified_gmt":"2024-08-23T14:55:03","slug":"ondas-sonoras","status":"publish","type":"page","link":"https:\/\/fisicaevestibular.com.br\/novo\/ondulatoria\/acustica\/ondas-sonoras\/","title":{"rendered":"Ondas Sonoras"},"content":{"rendered":"

Ondas Sonoras<\/b><\/span><\/span><\/span><\/p>\n

Ac\u00fastica<\/b><\/span><\/span><\/span><\/p>\n

Ac\u00fastica \"\"<\/b><\/span><\/span><\/span> <\/b>Parte da f\u00edsica <\/b><\/span><\/span><\/span>que estuda o <\/b><\/span><\/span><\/span>som e suas diversas manifesta\u00e7\u00f5es. Mais especificamente,<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

ac\u00fastica f\u00edsica estuda a parte material do fen\u00f4meno sonoro, <\/b><\/span><\/span><\/span>enquanto a <\/b><\/span><\/span><\/span>psicoac\u00fastica<\/b><\/span><\/span><\/span> trata da <\/b><\/span><\/span><\/span>percep\u00e7\u00e3o do fen\u00f4meno sonoro pelos sentidos.<\/b><\/span><\/span><\/span><\/p>\n

A <\/b><\/span><\/span><\/span>ondulat\u00f3ria \u00e9 <\/b><\/span><\/span><\/span>a parte da f\u00edsica <\/b><\/span><\/span><\/span>que estuda os fen\u00f4menos <\/b><\/span><\/span><\/span>que se apresentam<\/b><\/span><\/span><\/span> em formas de ondas<\/b><\/span><\/span><\/span> e, como <\/b><\/span><\/span><\/span>o som \u00e9 resultado da percep\u00e7\u00e3o de dist\u00farbios das mol\u00e9culas de um meio <\/b><\/span><\/span><\/span>em um certo espa\u00e7o de tempo, <\/b><\/span><\/span><\/span>esses dist\u00farbios<\/b><\/span><\/span><\/span>, por sua vez, apresentam-se em <\/b><\/span><\/span><\/span>forma de ondas <\/b><\/span><\/span><\/span>em sua <\/b><\/span><\/span><\/span>propaga\u00e7\u00e3o pelo meio, <\/b><\/span><\/span><\/span>e s\u00e3o <\/b><\/span><\/span><\/span>denominados de ondas sonoras.<\/b><\/span><\/span><\/span><\/p>\n

Ondas sonoras<\/b><\/span><\/span><\/span><\/p>\n

As <\/span><\/span><\/span>ondas de press\u00e3o <\/b><\/span><\/span><\/span>que caracterizam <\/b><\/span><\/span><\/span>o som, <\/b><\/span><\/span><\/span>denominadas<\/b><\/span><\/span><\/span> <\/b>ondas sonoras s\u00e3o ondas mec\u00e2nicas (<\/b><\/span><\/span><\/span>necessitam de um <\/b><\/span><\/span><\/span>meio material para se propagar)<\/b><\/span><\/span><\/span> <\/b>longitudinais (<\/b><\/span><\/span><\/span>a <\/b><\/span><\/span><\/span>dire\u00e7\u00e3o de vibra\u00e7\u00e3o coincide com a dire\u00e7\u00e3o de propaga\u00e7\u00e3o).<\/b><\/span><\/span><\/span> <\/b><\/p>\n

N\u00e3o se propagam no v\u00e1cuo <\/b><\/span><\/span><\/span>(n\u00e3o tem meio material para sua propaga\u00e7\u00e3o).<\/b><\/span><\/span><\/span><\/p>\n

S\u00e3o <\/b><\/span><\/span><\/span>produzidas por qualquer movimento vibrat\u00f3rio <\/b><\/span><\/span><\/span>e <\/b><\/span><\/span><\/span>expandem-se no espa\u00e7o <\/b><\/span><\/span><\/span>(tr\u00eas dimens\u00f5es) por<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

meio de <\/b><\/span><\/span><\/span>compress\u00f5es e rarefa\u00e7\u00f5es, <\/b><\/span><\/span><\/span>at\u00e9 chegarem aos <\/b><\/span><\/span><\/span>nossos ouvidos, <\/b><\/span><\/span><\/span>onde os <\/b><\/span><\/span><\/span>t\u00edmpanos, por<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

resson\u00e2ncia, s\u00e3o induzidos a vibrar com a mesma freq\u00fc\u00eancia da fonte e nos causam a sensa\u00e7\u00e3o fisiol\u00f3gica do som.<\/b><\/span><\/span><\/span><\/p>\n

A <\/b><\/span><\/span><\/span>faixa m\u00e9dia de freq\u00fc\u00eancias aud\u00edveis <\/b><\/span><\/span><\/span>para um <\/b><\/span><\/span><\/span>ouvido humano normal <\/b><\/span><\/span><\/span>varia de <\/b><\/span><\/span><\/span>20Hz \u00a0at\u00e9 20.000Hz.<\/b><\/span><\/span><\/span><\/p>\n

Ondas<\/b><\/span><\/span><\/span> com <\/b><\/span><\/span><\/span>freq\u00fc\u00eancias inferiores a 20Hz s\u00e3o os infra-sons e superiores a 20.000Hz s\u00e3o os ultra-sons.<\/b><\/span><\/span><\/span> <\/b>\"\"<\/p>\n

As <\/b><\/span><\/span><\/span>ondas infra-s\u00f4nicas <\/b><\/span><\/span><\/span>e <\/b><\/span><\/span><\/span>ultra-s\u00f4nicas n\u00e3o s\u00e3o aud\u00edveis pelo ouvido humano, mas existem <\/b><\/span><\/span><\/span>animais<\/b><\/span><\/span><\/span> (toupeira e elefante, por exemplo) que <\/b><\/span><\/span><\/span>s\u00e3o de captar os infra sons,<\/b><\/span><\/span><\/span> conseguindo ouvir as <\/b><\/span><\/span><\/span>ondas dos tremores de terra <\/b><\/span><\/span><\/span>(poucos Hz). <\/b><\/span><\/span><\/span><\/p>\n

J\u00e1 os <\/b><\/span><\/span><\/span>ultra-sons <\/b><\/span><\/span><\/span>podem ser ouvidos <\/b><\/span><\/span><\/span>por certos animais como morcego <\/b><\/span><\/span><\/span>(at\u00e9 160.000 Hz)<\/b><\/span><\/span><\/span>, o c\u00e3o e o <\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

gato <\/b><\/span><\/span><\/span>(at\u00e9 40.000 Hz) e tamb\u00e9m <\/b><\/span><\/span><\/span>utilizados na medicina (ecocardiografia, ultra-sonografia obst\u00e9trica, etc) .<\/b><\/span><\/span><\/span><\/p>\n

Velocidade do som<\/b><\/span><\/span><\/span><\/p>\n

A <\/b><\/span><\/span><\/span>maioria dos sons<\/b><\/span><\/span><\/span> chega ao <\/b><\/span><\/span><\/span>ouvido transmitido <\/b><\/span><\/span><\/span>pelo <\/b><\/span><\/span><\/span>ar, <\/b><\/span><\/span><\/span>(meio de transmiss\u00e3o), que, <\/b><\/span><\/span><\/span>quanto mais denso \u00e9 melhor transmissor,<\/b><\/span><\/span><\/span> pois <\/b><\/span><\/span><\/span>as mol\u00e9culas est\u00e3o mais pr\u00f3ximas transmitindo melhor a energia <\/b><\/span><\/span><\/span>de <\/b><\/span><\/span><\/span>umas para as outras.<\/b><\/span><\/span><\/span><\/p>\n

Por esse <\/b><\/span><\/span><\/span>motivo,<\/b><\/span><\/span><\/span> a <\/b><\/span><\/span><\/span>velocidade do som nos s\u00f3lidos<\/b><\/span><\/span><\/span> \u00e9 <\/b><\/span><\/span><\/span>maior do que nos l\u00edquidos <\/b><\/span><\/span><\/span>que por sua vez \u00e9 <\/b><\/span><\/span><\/span>maior que nos gases. \u00a0<\/b><\/span><\/span><\/span> \u00a0<\/b><\/span><\/span><\/span>\"\"<\/p>\n

A <\/b><\/span><\/span><\/span>velocidade de propaga\u00e7\u00e3o <\/b><\/span><\/span><\/span>do som <\/b><\/span><\/span><\/span>num dado meio depende da temperatura <\/b><\/span><\/span><\/span>em que <\/b><\/span><\/span><\/span>esse meio se encontra.<\/b><\/span><\/span><\/span><\/p>\n

Assim, verifica-se <\/b><\/span><\/span><\/span>um <\/b><\/span><\/span><\/span>aumento <\/b><\/span><\/span><\/span>na velocidade de propaga\u00e7\u00e3o do som num dado meio <\/b><\/span><\/span><\/span>quando a <\/b><\/span><\/span><\/span>temperatura do mesmo <\/b><\/span><\/span><\/span>aumenta <\/b><\/span><\/span><\/span>(<\/b><\/span><\/span><\/span>maior agita\u00e7\u00e3o das part\u00edculas).<\/b><\/span><\/span><\/span><\/p>\n

Isso ocorre na <\/b><\/span><\/span><\/span>gama de temperaturas pr\u00f3ximas<\/b><\/span><\/span><\/span> \u00e0 temperatura ambiente.<\/b><\/span><\/span><\/span><\/p>\n

Veja na tabela que, por exemplo, a <\/b><\/span><\/span><\/span>velocidade do som no ar a 0<\/b><\/span><\/span><\/span>o<\/b><\/span><\/span><\/sup><\/span>C (331 m\/s) \u00e9 menor que a no ar a 15<\/b><\/span><\/span><\/span>o<\/b><\/span><\/span><\/sup><\/span>C (340 m\/s). <\/b><\/span><\/span><\/span><\/p>\n

Compara\u00e7\u00e3o entre a velocidade do som e a velocidade da luz<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

Equa\u00e7\u00e3o fundamental da ondulat\u00f3ria para uma onda sonora<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

Devido \u00e0 sua <\/b><\/span><\/span><\/span>natureza longitudinal<\/b><\/span><\/span><\/span>, o som <\/b><\/span><\/span><\/span>n\u00e3o pode ser polarizado,<\/b><\/span><\/span><\/span> mas como em <\/b><\/span><\/span><\/span>qualquer onda sonora,<\/b><\/span><\/span><\/span> <\/b>podem ocorrer\u00a0 <\/b><\/span><\/span><\/span>os demais fen\u00f4menos, como <\/b><\/span><\/span><\/span>difra\u00e7\u00e3o, reflex\u00e3o, refra\u00e7\u00e3o, interfer\u00eancia e efeito Doppler.<\/b><\/span><\/span><\/span><\/p>\n

Reflex\u00e3o do som<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

A <\/b><\/span><\/span><\/span>reflex\u00e3o do som <\/b><\/span><\/span><\/span>\u00e9 um <\/b><\/span><\/span><\/span>fen\u00f4meno <\/b><\/span><\/span><\/span>que ocorre quando o <\/b><\/span><\/span><\/span>som<\/b><\/span><\/span><\/span> que <\/b><\/span><\/span><\/span>estava se propagando num meio,<\/b><\/span><\/span><\/span><\/p>\n

atinge uma <\/b><\/span><\/span><\/span>superf\u00edcie refletora e retorna ao meio de origem. <\/b><\/span><\/span><\/span><\/p>\n

Esse <\/b><\/span><\/span><\/span>fen\u00f4meno d\u00e1 origem ao eco e a reverbera\u00e7\u00e3o.<\/b><\/span><\/span><\/span><\/p>\n

Eco<\/b><\/span><\/span><\/span><\/p>\n

O <\/b><\/span><\/span><\/span>eco <\/b><\/span><\/span><\/span>\u00e9 um <\/b><\/span><\/span><\/span>fen\u00f4meno em que conseguimos ouvir nitidamente um som refletido por obst\u00e1culos refletores, uma ou mais vezes sucessivas.<\/b><\/span><\/span><\/span>\"\"<\/p>\n

Nosso ouvido <\/b><\/span><\/span><\/span>s\u00f3 consegue <\/b><\/span><\/span><\/span>distinguir dois sons sucessivos <\/b><\/span><\/span><\/span>num intervalo de tempo<\/b><\/span><\/span><\/span> igual ou maior que 0,10 segundos.<\/b><\/span><\/span><\/span><\/p>\n

Sendo a <\/b><\/span><\/span><\/span>velocidade do som no ar de 340m\/s, <\/b><\/span><\/span><\/span>temos que <\/b><\/span><\/span><\/span>V = \u0394S\/\u0394t\u00a0 \"\"<\/b><\/span><\/span><\/span>\u00a0 340=\u0394S\/0,1\u00a0 \"\"\u00a0<\/b><\/span><\/span><\/span>\u0394S=34m<\/b><\/span><\/span><\/span> <\/b>(ida e volta). <\/b><\/span><\/span><\/span><\/p>\n

Assim, <\/b><\/span><\/span><\/span>uma pessoa <\/b><\/span><\/span><\/span>consegue ouvir o eco de sua pr\u00f3pria voz<\/b><\/span><\/span><\/span> se estiver afastada do obst\u00e1culo refletor de, no m\u00ednimo, <\/b><\/span><\/span><\/span>17m.<\/b><\/span><\/span><\/span><\/p>\n

Reverbera\u00e7\u00e3o<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

Reverbera\u00e7\u00e3o\u00a0\"\"<\/b><\/span><\/span><\/span> <\/b>ocorre quando o som direto e refletido se superp\u00f5e chegando juntos ao ouvido, <\/b><\/span><\/span><\/span>o <\/b><\/span><\/span><\/span><\/p>\n

que ocorre quando a <\/b><\/span><\/span><\/span>superf\u00edcie refletora estiver a uma <\/b><\/span><\/span><\/span>dist\u00e2ncia menor que 17m da fonte emissora.<\/b><\/span><\/span><\/span> <\/b><\/p>\n

Os <\/b><\/span><\/span><\/span>sons diminuem ou aumentam<\/b><\/span><\/span><\/span> <\/b>de intensidade e ficam indistintos, <\/b><\/span><\/span><\/span>pois <\/b><\/span><\/span><\/span>chegam muitas reflex\u00f5es<\/b><\/span><\/span><\/span> ao ouvinte e ele <\/b><\/span><\/span><\/span>n\u00e3o consegue distinguir umas das outras.<\/b><\/span><\/span><\/span><\/p>\n

Sonar<\/b><\/span><\/span><\/span><\/p>\n

Sonar<\/b><\/span><\/span><\/span>\u00a0\"\" trata-se de um <\/b><\/span><\/span><\/span>dispositivo que emite ultra-sons, <\/b><\/span><\/span><\/span>que <\/b><\/span><\/span><\/span>chegam aos objetos, sofrem reflex\u00e3o e captam os ecos, permitindo localiza-los atrav\u00e9s da medida do tempo entre a emiss\u00e3o e a recep\u00e7\u00e3o do som sendo conhecida a velocidade de propaga\u00e7\u00e3o do som na \u00e1gua.<\/b><\/span><\/span><\/span>\"\"<\/p>\n

Muito utilizado na <\/b><\/span><\/span><\/span>orienta\u00e7\u00e3o da navega\u00e7\u00e3o fornecendo o perfil do fundo do mar, na localiza\u00e7\u00e3o de cardumes.<\/b><\/span><\/span><\/span><\/p>\n

Para se obter <\/b><\/span><\/span><\/span>imagens das partes externas e internas de qualquer objeto <\/b><\/span><\/span><\/span>(navios, submarinos, etc) <\/b><\/span><\/span><\/span>imersos no fundo do mar,deve-se utilizar o som atrav\u00e9s do ultra som enviado pelo sonar\u00a0 \"\"<\/b><\/span><\/span><\/span>\u00a0 o <\/b><\/span><\/span><\/span>som consegue passar pela superf\u00edcie dos sedimentos, penetrando nas mesmas, e conseguir<\/b><\/span><\/span><\/span><\/p>\n

definir a geometria das camadas internas atrav\u00e9s dos ecos,<\/b><\/span><\/span><\/span> que chegam em <\/b><\/span><\/span><\/span>instantes diferentes ao receptor na superf\u00edcie, <\/b><\/span><\/span><\/span>conseguindo assim uma <\/b><\/span><\/span><\/span>figura em 3D do elemento naufragado.<\/b><\/span><\/span><\/span>\"\"<\/p>\n

A luz n\u00e3o \u00e9 conveniente,<\/b><\/span><\/span><\/span> j\u00e1 que \u00e9 <\/b><\/span><\/span><\/span>atenuada<\/b><\/span><\/span><\/span> (refletida ou absorvida) nas <\/b><\/span><\/span><\/span>primeiras camadas iniciais dos sedimentos, n\u00e3o conseguindo penetrar nos mesmos, e seriam visualizadas apenas os formatos superficiais dos sedimentos.<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

O mesmo acontece quando voc\u00ea <\/b><\/span><\/span><\/span>quer estudar as partes internas de metais <\/b><\/span><\/span><\/span>(estrutura dos materiais).<\/b><\/span><\/span><\/span><\/p>\n

Radar\u00a0<\/b><\/span><\/span><\/span><\/p>\n

Radar <\/b><\/span><\/span><\/span>\u00a0\"\" <\/b><\/span><\/span><\/span>funciona como o sonar, <\/b><\/span><\/span><\/span>mas <\/b><\/span><\/span><\/span>em vez de ondas ultra-s\u00f4nicas, emite ondas <\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

eletromagn\u00e9ticas que s\u00e3o refletidas por objetos distantes, permitindo assim, sua localiza\u00e7\u00e3o.<\/b><\/span><\/span><\/span><\/p>\n

Ecografia ou ultra-sonografia\u00a0<\/b><\/span><\/span><\/span><\/p>\n

Ecografia ou ultra-sonografia\u00a0\"\"<\/b><\/span><\/span><\/span> \u00e9 um <\/b><\/span><\/span><\/span>m\u00e9todo diagn\u00f3stico <\/b><\/span><\/span><\/span>que permite<\/b><\/span><\/span><\/span>, atrav\u00e9s do eco<\/b><\/span><\/span><\/span>, ver os <\/b><\/span><\/span><\/span>movimentos produzidos pelos<\/b><\/span><\/span><\/span>\"\"<\/p>\n

diversos \u00f3rg\u00e3os do interior do organismo.<\/b><\/span><\/span><\/span><\/p>\n

Quando o <\/b><\/span><\/span><\/span>ultra-som \u00e9 colocado, atrav\u00e9s do transdutor, <\/b><\/span><\/span><\/span>sobre a <\/b><\/span><\/span><\/span>pele do paciente, <\/b><\/span><\/span><\/span>os <\/b><\/span><\/span><\/span>sons<\/b><\/span><\/span><\/span> por ele <\/b><\/span><\/span><\/span>emitidos refletem-se nos \u00f3rg\u00e3os ou estruturas internas e retornam como ecos, <\/b><\/span><\/span><\/span>que s\u00e3o <\/b><\/span><\/span><\/span>sons <\/b><\/span><\/span><\/span>que o <\/b><\/span><\/span><\/span>transdutor modifica eletronicamente e os transforma em imagens.<\/b><\/span><\/span><\/span><\/p>\n

\u00a0<\/span><\/p>\n

O que voc\u00ea deve saber, informa\u00e7\u00f5es e dicas<\/b><\/span><\/span><\/span><\/p>\n

\"\" \u00a0<\/span>Entender as <\/b><\/span><\/span><\/span>informa\u00e7\u00f5es<\/b><\/span><\/span><\/span> acima <\/b><\/span><\/span><\/span>sobre <\/b><\/span><\/span><\/span>eco, reverbera\u00e7\u00e3o, sonar, radar e ultra-sonografia.<\/b><\/span><\/span><\/span><\/p>\n

\"\" Ondas sonoras \"\"<\/b><\/span><\/span><\/span> s\u00e3o <\/b><\/span><\/span><\/span>ondas mec\u00e2nicas <\/b><\/span><\/span><\/span>(necessitam de um meio material para se propagar) <\/b><\/span><\/span><\/span>longitudinais<\/b><\/span><\/span><\/span> (a dire\u00e7\u00e3o de vibra\u00e7\u00e3o coincide com a dire\u00e7\u00e3o de propaga\u00e7\u00e3o).<\/b><\/span><\/span><\/span><\/p>\n

N\u00e3o se propagam no v\u00e1cuo<\/b><\/span><\/span><\/span><\/p>\n

\"\" A <\/b><\/span><\/span><\/span>faixa m\u00e9dia de freq\u00fc\u00eancias aud\u00edveis <\/b><\/span><\/span><\/span>para um <\/b><\/span><\/span><\/span>ouvido humano normal <\/b><\/span><\/span><\/span>varia de <\/b><\/span><\/span><\/span>20Hz \u00a0at\u00e9 20.000Hz.<\/b><\/span><\/span><\/span><\/p>\n

Ondas<\/b><\/span><\/span><\/span> com <\/b><\/span><\/span><\/span>freq\u00fc\u00eancias inferiores a 20Hz s\u00e3o os infra-sons e superiores a 20.000Hz s\u00e3o os ultra-sons.<\/b><\/span><\/span><\/span> <\/b>\"\"<\/p>\n

As <\/b><\/span><\/span><\/span>ondas infra-s\u00f4nicas <\/b><\/span><\/span><\/span>e <\/b><\/span><\/span><\/span>ultra-s\u00f4nicas n\u00e3o s\u00e3o aud\u00edveis pelo ouvido humano, mas existem <\/b><\/span><\/span><\/span>animais<\/b><\/span><\/span><\/span> (toupeira e elefante, por exemplo) que <\/b><\/span><\/span><\/span>s\u00e3o de captar os infra sons,<\/b><\/span><\/span><\/span> conseguindo ouvir as <\/b><\/span><\/span><\/span>ondas dos tremores de terra <\/b><\/span><\/span><\/span>(poucos Hz). <\/b><\/span><\/span><\/span><\/p>\n

J\u00e1 os <\/b><\/span><\/span><\/span>ultra-sons <\/b><\/span><\/span><\/span>podem ser ouvidos <\/b><\/span><\/span><\/span>por certos animais como morcego <\/b><\/span><\/span><\/span>(at\u00e9 160.000 Hz)<\/b><\/span><\/span><\/span>, o c\u00e3o e o <\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

gato <\/b><\/span><\/span><\/span>(at\u00e9 40.000 Hz) e tamb\u00e9m <\/b><\/span><\/span><\/span>utilizados na medicina (ecocardiografia, ultra-sonografia obst\u00e9trica, etc) .<\/b><\/span><\/span><\/span><\/p>\n

\"\" Compara\u00e7\u00e3o entre a velocidade do som e a velocidade da luz<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

\"\" Equa\u00e7\u00e3o fundamental da ondulat\u00f3ria para uma onda sonora<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

\"\" A <\/b><\/span><\/span><\/span>freq\u00fc\u00eancia \u00e9 caracter\u00edstica da onda. <\/b><\/span><\/span><\/span>Se a <\/b><\/span><\/span><\/span>fonte \u00e9 a mesma, a <\/b><\/span><\/span><\/span>freq\u00fc\u00eancia da onda \u00e9 a mesma da<\/b><\/span><\/span><\/span> <\/b>fonte,<\/b><\/span><\/span><\/span> independente do meio onde ela estiver se propagando.<\/b><\/span><\/span><\/span><\/p>\n

\"\" \u00a0Eco \u00a0\"\" <\/b><\/span><\/span><\/span> fen\u00f4meno em que <\/b><\/span><\/span><\/span>conseguimos ouvir nitidamente um som refletido por obst\u00e1culos refletores, uma ou mais vezes sucessivas.<\/b><\/span><\/span><\/span> <\/b><\/p>\n

Nosso <\/b><\/span><\/span><\/span>ouvido s\u00f3 consegue distinguir dois sons sucessivos num intervalo de tempo igual ou maior que 0,10segundos. <\/b><\/span><\/span><\/span>Assim, uma <\/b><\/span><\/span><\/span>pessoa consegue ouvir o eco de sua pr\u00f3pria voz se estiver afastada do obst\u00e1culo refletor de, no m\u00ednimo, 17m.<\/b><\/span><\/span><\/span><\/p>\n

\"\" Alguns <\/b><\/span><\/span><\/span>exerc\u00edcios interessantes <\/b><\/span><\/span><\/span>para que voc\u00ea possa <\/b><\/span><\/span><\/span>observar e entender a resolu\u00e7\u00e3o:<\/b><\/span><\/span><\/span><\/p>\n

01-<\/b><\/span><\/span><\/span> <\/b>(UNESP-SP)<\/b><\/span><\/span><\/span> <\/b>Nas <\/b><\/span><\/span><\/span>\u00faltimas d\u00e9cadas, <\/b><\/span><\/span><\/span>o cinema tem produzido <\/b><\/span><\/span><\/span>in\u00fameros filmes de fic\u00e7\u00e3o cient\u00edfica <\/b><\/span><\/span><\/span>com cenas de guerras espaciais, <\/b><\/span><\/span><\/span>como Guerra nas estrelas.<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

\u00a0<\/span>Com exce\u00e7\u00e3o de 2001, uma odiss\u00e9ia no espa\u00e7o, <\/b><\/span><\/span><\/span>essas <\/b><\/span><\/span><\/span>cenas apresentam explos\u00f5es com estrondos impressionantes,<\/b><\/span><\/span><\/span> al\u00e9m de <\/b><\/span><\/span><\/span>efeitos luminosos espetaculares, <\/b><\/span><\/span><\/span>tudo isso <\/b><\/span><\/span><\/span>no espa\u00e7o interplanet\u00e1rio.<\/b><\/span><\/span><\/span><\/p>\n

a) <\/b><\/span><\/span><\/span>Comparando <\/b><\/span><\/span><\/span>Guerra nas estrelas, que apresenta efeitos sonoros e explos\u00e3o, <\/b><\/span><\/span><\/span>com <\/b><\/span><\/span><\/span>2001, uma odiss\u00e9ia no espa\u00e7o<\/b><\/span><\/span><\/span>, que <\/b><\/span><\/span><\/span>n\u00e3o os apresenta, <\/b><\/span><\/span><\/span>qual deles <\/b><\/span><\/span><\/span>est\u00e1 <\/b><\/span><\/span><\/span>de acordo com as <\/b><\/span><\/span><\/span>leis da f\u00edsica? Justifique.<\/b><\/span><\/span><\/span><\/p>\n

b) <\/b><\/span><\/span><\/span>E quanto aos <\/b><\/span><\/span><\/span>efeitos luminosos que todos apresentam? Justifique.<\/b><\/span><\/span><\/span><\/p>\n

Resolu\u00e7\u00e3o:<\/b><\/span><\/span><\/span><\/p>\n

a) 2001, Uma odiss\u00e9ia no espa\u00e7o, <\/b><\/span><\/span><\/span>est\u00e1 de acordo com as leis da f\u00edsica, <\/b><\/span><\/span><\/span>pois o som n\u00e3o se propaga no v\u00e1cuo do espa\u00e7o interplanet\u00e1rio.<\/b><\/span><\/span><\/span><\/p>\n

b) <\/b><\/span><\/span><\/span>Os <\/b><\/span><\/span><\/span>dois est\u00e3o corretos, pois a luz se propaga no v\u00e1cuo.<\/b><\/span><\/span><\/span><\/p>\n

02<\/b><\/span><\/span><\/span>– <\/b><\/span><\/span><\/span>(ITA-SP) <\/b><\/span><\/span><\/span>Mediante um <\/b><\/span><\/span><\/span>processo eletromec\u00e2nico percute-se um gongo a cada 0,5s<\/b><\/span><\/span><\/span>. Uma <\/b><\/span><\/span><\/span>pessoa <\/b><\/span><\/span><\/span>parada <\/b><\/span><\/span><\/span>bem pr\u00f3xima ao gongo v\u00ea e ouve as batidas simultaneamente. Afastando-se <\/b><\/span><\/span><\/span>um pouco do gongo, ela <\/b><\/span><\/span><\/span>passa a ouvir o som um pouco depois de sua batida; <\/b><\/span><\/span><\/span>entretanto, quando a <\/b><\/span><\/span><\/span>pessoa estiver afastada uma dist\u00e2ncia de 172m do gongo, novamente som e imagem se tornam simult\u00e2neos. <\/b><\/span><\/span><\/span>\"\"<\/p>\n

Determine a <\/b><\/span><\/span><\/span>velocidade do som nas condi\u00e7\u00f5es da experi\u00eancia.<\/b><\/span><\/span><\/span><\/p>\n

Resolu\u00e7\u00e3o:<\/b><\/span><\/span><\/span><\/p>\n

Quando, <\/b><\/span><\/span><\/span>novamente, som e imagem forem simult\u00e2neos, <\/b><\/span><\/span><\/span>a <\/b><\/span><\/span><\/span>pessoa estar\u00e1 ouvindo o som da pancada anterior,<\/b><\/span><\/span><\/span> que estar\u00e1 percorrendo a <\/b><\/span><\/span><\/span>dist\u00e2ncia de 172m em 0,5 s.<\/b><\/span><\/span><\/span><\/p>\n

V = \u0394S\/\u0394t\u00a0 \"\"<\/b><\/span><\/span><\/span>\u00a0 V=172\/0,5\u00a0 \"\"\u00a0\u00a0<\/b><\/span><\/span><\/span>V = 344 m\/s.<\/b><\/span><\/span><\/span><\/p>\n

03-<\/b><\/span><\/span><\/span> <\/b>(MACKENZIE-SP)<\/b><\/span><\/span><\/span> <\/b>Um <\/b><\/span><\/span><\/span>ferreiro golpeia<\/b><\/span><\/span><\/span>, com a marreta, uma <\/b><\/span><\/span><\/span>l\u00e2mina de ferro, em ritmo uniforme, a cada 0,9 s.<\/b><\/span><\/span><\/span><\/p>\n

Um <\/b><\/span><\/span><\/span>observador, afastado desse ferreiro v\u00ea, <\/b><\/span><\/span><\/span>com um <\/b><\/span><\/span><\/span>bin\u00f3culo,<\/b><\/span><\/span><\/span> a <\/b><\/span><\/span><\/span>marreta atingir o ferro e ouve o som das batidas simultaneamente.<\/b><\/span><\/span><\/span>\"\"<\/p>\n

A <\/b><\/span><\/span><\/span>velocidade do som<\/b><\/span><\/span><\/span>, nas condi\u00e7\u00f5es do local, \u00e9 <\/b><\/span><\/span><\/span>330m\/s. Calcule<\/b><\/span><\/span><\/span> a <\/b><\/span><\/span><\/span>menor dist\u00e2ncia entre o ferreiro e o observador. <\/b><\/span><\/span><\/span><\/p>\n

Resolu\u00e7\u00e3o:<\/b><\/span><\/span><\/span><\/p>\n

O <\/b><\/span><\/span><\/span>som chega ao observador com atraso <\/b><\/span><\/span><\/span>e <\/b><\/span><\/span><\/span>som e imagem <\/b><\/span><\/span><\/span>ser\u00e3o <\/b><\/span><\/span><\/span>simult\u00e2neos quando o atraso <\/b><\/span><\/span><\/span>for um <\/b><\/span><\/span><\/span>m\u00faltiplo do per\u00edodo das marteladas,<\/b><\/span><\/span><\/span> ou seja, <\/b><\/span><\/span><\/span>a cada 0,9s, 1,8s, 2,7s, etc. <\/b><\/span><\/span><\/span><\/p>\n

No caso, a <\/b><\/span><\/span><\/span>menor dist\u00e2ncia ocorre com um atraso de\u00a0\u0394t = 0,9 s.<\/b><\/span><\/span><\/span><\/p>\n

V = \u0394S\/\u0394t\u00a0 \"\"<\/b><\/span><\/span><\/span>\u00a0 330 = \u0394S\/0,9\u00a0 \"\"\u00a0\u00a0<\/b><\/span><\/span><\/span>\u0394S = 297 m.<\/b><\/span><\/span><\/span><\/p>\n

04-<\/b><\/span><\/span><\/span> <\/b>(FUVEST-SP)<\/b><\/span><\/span><\/span> <\/b>Um <\/b><\/span><\/span><\/span>alto-falante <\/b><\/span><\/span><\/span>emite um <\/b><\/span><\/span><\/span>som cuja freq\u00fc\u00eancia F<\/b><\/span><\/span><\/span>, expressa em <\/b><\/span><\/span><\/span>Hz<\/b><\/span><\/span><\/span>, varia em <\/b><\/span><\/span><\/span>fun\u00e7\u00e3o do tempo t na forma F(t) = 1.000 + 200t.<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

Num <\/b><\/span><\/span><\/span>dado momento, o alto-falante est\u00e1 emitindo um som com uma freq\u00fc\u00eancia F<\/b><\/span><\/span><\/span>1 <\/b><\/span><\/span><\/sub><\/span>= 1.080 Hz. <\/b><\/span><\/span><\/span><\/p>\n

Nesse <\/b><\/span><\/span><\/span>mesmo instante, uma pessoa P, parada a uma dist\u00e2ncia D = 34 m do alto-falante<\/b><\/span><\/span><\/span>, est\u00e1 <\/b><\/span><\/span><\/span>ouvindo<\/b><\/span><\/span><\/span> um <\/b><\/span><\/span><\/span>som com freq\u00fc\u00eancia F<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span>,<\/b><\/span><\/span><\/span> aproximadamente, <\/b><\/span><\/span><\/span>igual a quantos Hz? <\/b><\/span><\/span><\/span>(velocidade do som no ar = 340 m\/s)<\/b><\/span><\/span><\/span><\/p>\n

Resolu\u00e7\u00e3o:<\/b><\/span><\/span><\/span><\/p>\n

C\u00e1lculo do <\/b><\/span><\/span><\/span>instante em que o alto-falante est\u00e1 emitindo o som de freq\u00fc\u00eancia F<\/b><\/span><\/span><\/span>1 <\/b><\/span><\/span><\/sub><\/span>= 1.080 Hz \"\"<\/b><\/span><\/span><\/span><\/p>\n

F(t) = 1000 + 200t\u00a0 \"\"<\/b><\/span><\/span><\/span>\u00a0 1080 = 1000 + 200t\u00a0 \"\"\u00a0 <\/b><\/span><\/span><\/span>t<\/b><\/span><\/span><\/span>1<\/b><\/span><\/span><\/sub><\/span> = 0,4 s.<\/b><\/span><\/span><\/span><\/p>\n

C\u00e1lculo do <\/b><\/span><\/span><\/span>intervalo de tempo que qualquer som com V = 340 m\/s emitido pela fonte demora\u00a0 para chegar \u00e0 pessoa P que est\u00e1 a D = 34 m da fonte \"\" V = \u0394S\/\u0394t\u00a0 \"\"<\/b><\/span><\/span><\/span>\u00a0 340 = 34\/\u0394t\u00a0 \"\"\u00a0\u00a0<\/b><\/span><\/span><\/span>\u0394t = 0,1s.<\/b><\/span><\/span><\/span><\/p>\n

Assim, o <\/b><\/span><\/span><\/span>som que est\u00e1 sendo ouvido pela pessoa no instante t<\/b><\/span><\/span><\/span>1<\/b><\/span><\/span><\/sub><\/span> = 0,4s foi emitido pela <\/b><\/span><\/span><\/span>fonte no instante <\/b><\/span><\/span><\/span>t<\/b><\/span><\/span><\/span>o<\/b><\/span><\/span><\/sub><\/span> <\/b>= t<\/b><\/span><\/span><\/span>1<\/b><\/span><\/span><\/sub><\/span> \u2013 \u2206t = 0,4s \u2013 0,1s <\/b><\/span><\/span><\/span>= 0,3s<\/b><\/span><\/span><\/span>. <\/b><\/span><\/span><\/span><\/p>\n

A <\/b><\/span><\/span><\/span>freq\u00fc\u00eancia desse som \u00e9 dada por f = 1000 + 200 . 0,3 <\/b><\/span><\/span><\/span> \"\" F = <\/b><\/span><\/span><\/span>1000 + 200.0,3\u00a0 \"\"\u00a0\u00a0<\/b><\/span><\/span><\/span>F<\/b><\/span><\/span><\/span>2 <\/b><\/span><\/span><\/sub><\/span>= 1.060 Hz.<\/b><\/span><\/span><\/span><\/p>\n

 <\/p>\n

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

Ondas Sonoras Ac\u00fastica Ac\u00fastica Parte da f\u00edsica que estuda o som e suas diversas manifesta\u00e7\u00f5es. Mais especificamente, ac\u00fastica f\u00edsica estuda a parte material do fen\u00f4meno sonoro, enquanto a psicoac\u00fastica trata da percep\u00e7\u00e3o do fen\u00f4meno sonoro pelos sentidos. A ondulat\u00f3ria \u00e9 a parte da f\u00edsica que estuda os fen\u00f4menos que se apresentam em formas de ondas e, como o som \u00e9<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":2325,"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-2327","page","type-page","status-publish","hentry"],"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/pages\/2327","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=2327"}],"version-history":[{"count":3,"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/pages\/2327\/revisions"}],"predecessor-version":[{"id":2334,"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/pages\/2327\/revisions\/2334"}],"up":[{"embeddable":true,"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/pages\/2325"}],"wp:attachment":[{"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/media?parent=2327"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}