{"id":2618,"date":"2016-11-11T02:30:12","date_gmt":"2016-11-11T02:30:12","guid":{"rendered":"http:\/\/fisicaevestibular.com.br\/novo\/?page_id=2618"},"modified":"2024-09-02T15:00:37","modified_gmt":"2024-09-02T15:00:37","slug":"estatica","status":"publish","type":"page","link":"https:\/\/fisicaevestibular.com.br\/novo\/raciocinio-logico\/estatica\/","title":{"rendered":"Est\u00e1tica"},"content":{"rendered":"

Est\u00e1tica<\/b><\/span><\/span><\/span><\/p>\n

Como esse conte\u00fado envolve muita teoria, em caso de d\u00favidas voc\u00ea pode encontr\u00e1-la em <\/b><\/span><\/span><\/span><\/p>\n

fisicaevestibular.com.br \u2013 Mec\u00e2nica \u2013 Est\u00e1tica)<\/b><\/span><\/span><\/span><\/p>\n

01- (UNIFOR-CE)<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

\u00a0Com <\/b><\/span><\/span><\/span>6 peda\u00e7os iguais de corda<\/b><\/span><\/span><\/span> e <\/b><\/span><\/span><\/span>tr\u00eas corpos de mesma massa e mesmo formato, <\/b><\/span><\/span><\/span>um <\/b><\/span><\/span><\/span>estudante fez as montagens representadas abaixo.<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

Nos <\/b><\/span><\/span><\/span>peda\u00e7os de corda a intensidade da for\u00e7a de tra\u00e7\u00e3o <\/b><\/span><\/span><\/span>\u00e9<\/b><\/span><\/span><\/span><\/p>\n

(A) <\/b><\/span><\/span><\/span>a <\/b><\/span><\/span><\/span>mesma <\/b><\/span><\/span><\/span>nas montagens <\/b><\/span><\/span><\/span>1, 2 e 3.\u00a0<\/b><\/span><\/span><\/span>\u00a0\u00a0\u00a0\u00a0\u00a0 <\/b><\/span><\/span><\/span><\/p>\n

(B) maior<\/b><\/span><\/span><\/span> na montagem <\/b><\/span><\/span><\/span>3 que na 2.\u00a0\u00a0\u00a0\u00a0\u00a0 <\/b><\/span><\/span><\/span><\/p>\n

(C) maior<\/b><\/span><\/span><\/span> na montagem <\/b><\/span><\/span><\/span>2 que na 3.<\/b><\/span><\/span><\/span><\/p>\n

(D) <\/b><\/span><\/span><\/span>a <\/b><\/span><\/span><\/span>mesma <\/b><\/span><\/span><\/span>nas montagens <\/b><\/span><\/span><\/span>2 e 3 <\/b><\/span><\/span><\/span>e <\/b><\/span><\/span><\/span>menor<\/b><\/span><\/span><\/span> que <\/b><\/span><\/span><\/span>na 1.\u00a0\u00a0\u00a0\u00a0\u00a0 <\/b><\/span><\/span><\/span><\/p>\n

(E) <\/b><\/span><\/span><\/span>a <\/b><\/span><\/span><\/span>mesma<\/b><\/span><\/span><\/span> nas montagens <\/b><\/span><\/span><\/span>2 e 3 <\/b><\/span><\/span><\/span>e <\/b><\/span><\/span><\/span>maior<\/b><\/span><\/span><\/span> que <\/b><\/span><\/span><\/span>na 1.<\/b><\/span><\/span><\/span><\/p>\n

02-(MACKENZIE-SP)<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

Certo <\/b><\/span><\/span><\/span>corpo de massa 10,0 kg <\/b><\/span><\/span><\/span>est\u00e1 <\/b><\/span><\/span><\/span>suspenso por uma pequena argola, <\/b><\/span><\/span><\/span>que <\/b><\/span><\/span><\/span>pode deslizar, sem atrito, por um fio, supostamente ideal. <\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

Em uma <\/b><\/span><\/span><\/span>primeira situa\u00e7\u00e3o, <\/b><\/span><\/span><\/span>o corpo <\/b><\/span><\/span><\/span>encontra-se na posi\u00e7\u00e3o ilustrada na figura 1 <\/b><\/span><\/span><\/span>e, d<\/b><\/span><\/span><\/span>epois<\/b><\/span><\/span><\/span> de certo tempo, <\/b><\/span><\/span><\/span>encontra-se na posi\u00e7\u00e3o ilustrada na figura 2. <\/b><\/span><\/span><\/span><\/p>\n

O <\/b><\/span><\/span><\/span>trabalho realizado pela for\u00e7a peso,<\/b><\/span><\/span><\/span> entre <\/b><\/span><\/span><\/span>a posi\u00e7\u00e3o 1 e a posi\u00e7\u00e3o 2, <\/b><\/span><\/span><\/span>foi\u00a0\u00a0\u00a0 \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0<\/b><\/span><\/span><\/span><\/p>\n

a)\u00a0 2,40. 10<\/b><\/span><\/span><\/span>-1<\/b><\/span><\/span><\/sup><\/span>J\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 <\/b><\/span><\/span><\/span><\/p>\n

b) 2,45.10<\/b><\/span><\/span><\/span>-1<\/b><\/span><\/span><\/sup><\/span>J\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 <\/b><\/span><\/span><\/span><\/p>\n

c) 5,00.10<\/b><\/span><\/span><\/span>-1<\/b><\/span><\/span><\/sup><\/span>J\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 <\/b><\/span><\/span><\/span><\/p>\n

d) 2,40J\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 <\/b><\/span><\/span><\/span><\/p>\n

e) 2,45J<\/b><\/span><\/span><\/span><\/p>\n

03-(UFF-RJ)<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

\u00cdm\u00e3s <\/b><\/span><\/span><\/span>s\u00e3o frequentemente <\/b><\/span><\/span><\/span>utilizados para prender pequenos objetos\u00a0 em superf\u00edcies met\u00e1licas planas e verticais, como quadros de avisos e portas de geladeiras.<\/b><\/span><\/span><\/span><\/p>\n

Considere que <\/b><\/span><\/span><\/span>um \u00edm\u00e3, colado a um grampo, <\/b><\/span><\/span><\/span>esteja em <\/b><\/span><\/span><\/span>contato com a porta de uma geladeira. <\/b><\/span><\/span><\/span>Suponha que a <\/b><\/span><\/span><\/span>for\u00e7a magn\u00e9tica que o \u00edm\u00e3 faz sobre a superf\u00edcie da geladeira \u00e9 perpendicular a ela e tem m\u00f3dulo F<\/b><\/span><\/span><\/span>M<\/b><\/span><\/span><\/sub><\/span>.<\/b><\/span><\/span><\/span><\/p>\n

. O <\/b><\/span><\/span><\/span>conjunto im\u00e3\/grampo tem massa m<\/b><\/span><\/span><\/span>o<\/b><\/span><\/span><\/sub><\/span><\/p>\n

.O <\/b><\/span><\/span><\/span>coeficiente de atrito est\u00e1tico entre a superf\u00edcie da geladeira e a do \u00edm\u00e3 \u00e9\u00a0\u00a0\u03bc<\/b><\/span><\/span><\/span>e<\/b><\/span><\/span><\/sub><\/span><\/p>\n

.Uma <\/b><\/span><\/span><\/span>massa M <\/b><\/span><\/span><\/span>est\u00e1 <\/b><\/span><\/span><\/span>pendurada no grampo por um fio de massa desprez\u00edvel, como mostra a figura.<\/b><\/span><\/span><\/span>\"\"<\/p>\n

a) Desenhe no diagrama as for\u00e7as<\/b><\/span><\/span><\/span> que agem <\/b><\/span><\/span><\/span>sobre o conjunto \u00edm\u00e3\/grampo, identificando cada uma dessas for\u00e7as.<\/b><\/span><\/span><\/span><\/p>\n

b) <\/b><\/span><\/span><\/span>Qual o <\/b><\/span><\/span><\/span>maior valor da massa\u00a0 M\u00a0 que pode ser pendurada no grampo sem que o conjunto caia?<\/b><\/span><\/span><\/span><\/p>\n

04-(UPE-PE)<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

A <\/b><\/span><\/span><\/span>figura abaixo ilustra uma roda de raio R e massa m. <\/b><\/span><\/span><\/span><\/p>\n

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

Qual \u00e9 o <\/b><\/span><\/span><\/span>m\u00f3dulo da for\u00e7a horizontal\u00a0\"\", <\/b><\/span><\/span><\/span>necess\u00e1ria para <\/b><\/span><\/span><\/span>erguer a roda sobre um degrau de altura h = R\/2, quando aplicada no seu eixo?<\/b><\/span><\/span><\/span><\/p>\n

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

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

05-(UFPR-PR)<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

\"\"<\/p>\n

Uma <\/b><\/span><\/span><\/span>corrente composta <\/b><\/span><\/span><\/span>por <\/b><\/span><\/span><\/span>cinco elos est\u00e1 presa ao teto <\/b><\/span><\/span><\/span>por <\/b><\/span><\/span><\/span>meio de um barbante, <\/b><\/span><\/span><\/span>conforme mostra a <\/b><\/span><\/span><\/span>figura. \u00a0<\/b><\/span><\/span><\/span><\/p>\n

A <\/b><\/span><\/span><\/span>massa de cada elo \u00e9 de 200 g.<\/b><\/span><\/span><\/span><\/p>\n

a) <\/b><\/span><\/span><\/span>Fa\u00e7a um <\/b><\/span><\/span><\/span>diagrama de for\u00e7as para o terceiro elo, <\/b><\/span><\/span><\/span>identificando <\/b><\/span><\/span><\/span>cada uma das for\u00e7as que atuam sobre ele.<\/b><\/span><\/span><\/span><\/p>\n

b) <\/b><\/span><\/span><\/span>Calcule o <\/b><\/span><\/span><\/span>m\u00f3dulo de todas as for\u00e7as que est\u00e3o atuando nesse terceiro elo.<\/b><\/span><\/span><\/span><\/p>\n

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

06-(MACKENZIE-SP)<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

\"\"<\/p>\n

Um <\/b><\/span><\/span><\/span>quadro, pesando 36,0 N, <\/b><\/span><\/span><\/span>\u00e9 suspenso por um <\/b><\/span><\/span><\/span>fio ideal preso \u00e0s suas extremidades. <\/b><\/span><\/span><\/span><\/p>\n

Esse <\/b><\/span><\/span><\/span>fio se apoia em um prego fixo \u00e0 parede, <\/b><\/span><\/span><\/span>como mostra a <\/b><\/span><\/span><\/span>figura.<\/b><\/span><\/span><\/span> <\/b><\/p>\n

Desprezados <\/b><\/span><\/span><\/span>os atritos, a for\u00e7a de tra\u00e7\u00e3o no fio tem intensidade<\/b><\/span><\/span><\/span> de:<\/b><\/span><\/span><\/span><\/p>\n

a) <\/b><\/span><\/span><\/span>20,0 N\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0<\/b><\/span><\/span><\/span><\/p>\n

b) <\/b><\/span><\/span><\/span>22,5 N\u00a0\u00a0\u00a0\u00a0\u00a0 \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0<\/b><\/span><\/span><\/span><\/p>\n

c) <\/b><\/span><\/span><\/span>25,0 N\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0<\/b><\/span><\/span><\/span><\/p>\n

d) <\/b><\/span><\/span><\/span>27,5N\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0<\/b><\/span><\/span><\/span><\/p>\n

e) <\/b><\/span><\/span><\/span>30,0 N<\/b><\/span><\/span><\/span><\/p>\n

07-(PUC-SP)<\/b><\/span><\/span><\/span> <\/b>Para tentar <\/b><\/span><\/span><\/span>desencalhar um carro,<\/b><\/span><\/span><\/span> seu motorista <\/b><\/span><\/span><\/span>prende a extremidade de uma corda inextens\u00edvel e de peso desprez\u00edvel\u00a0ao p\u00e1ra choque <\/b><\/span><\/span><\/span>e a <\/b><\/span><\/span><\/span>outra extremidade a uma \u00e1rvore,<\/b><\/span><\/span><\/span> de modo que <\/b><\/span><\/span><\/span>a corda fique disposta horizontalmente com um comprimento livre de 10m. <\/b><\/span><\/span><\/span>\"\"<\/p>\n

No <\/b><\/span><\/span><\/span>meio da corda \u00e9 suspenso um corpo de 20N de peso. <\/b><\/span><\/span><\/span><\/p>\n

Nessas condi\u00e7\u00f5es, <\/b><\/span><\/span><\/span>observa-se que o ponto m\u00e9dio da corda desce de 0,2m. <\/b><\/span><\/span><\/span><\/p>\n

A <\/b><\/span><\/span><\/span>intensidade da for\u00e7a transmitida ao carro \u00e9,<\/b><\/span><\/span><\/span> aproximadamente de:<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

08-(FUVEST-SP)<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

Um <\/b><\/span><\/span><\/span>mesmo pacote <\/b><\/span><\/span><\/span>pode ser <\/b><\/span><\/span><\/span>carregado com cordas amarradas\u00a0 de v\u00e1rias maneiras. <\/b><\/span><\/span><\/span><\/p>\n

A <\/b><\/span><\/span><\/span>situa\u00e7\u00e3o, dentre as apresentadas, <\/b><\/span><\/span><\/span>em que as <\/b><\/span><\/span><\/span>cordas est\u00e3o sujeitas \u00e0 maior tens\u00e3o <\/b><\/span><\/span><\/span>\u00e9:<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

09- (UNICAMP-SP)<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

Quando um <\/b><\/span><\/span><\/span>homem est\u00e1 deitado numa rede <\/b><\/span><\/span><\/span>(de massa desprez\u00edvel), as <\/b><\/span><\/span><\/span>for\u00e7as que esta aplica na parede formam um \u00e2ngulo de 30\u00b0 com a horizontal, <\/b><\/span><\/span><\/span>e a <\/b><\/span><\/span><\/span>intensidade de cada uma \u00e9 de 60 kgf (ver figura)<\/b><\/span><\/span><\/span>\"\"<\/p>\n

a)<\/b><\/span><\/span><\/span> <\/b>Qual \u00e9 o <\/b><\/span><\/span><\/span>peso do homem?<\/b><\/span><\/span><\/span><\/p>\n

b) <\/b><\/span><\/span><\/span>O <\/b><\/span><\/span><\/span>gancho da parede foi mal instalado <\/b><\/span><\/span><\/span>e <\/b><\/span><\/span><\/span>resiste apenas at\u00e9 130 kgf. Quantas crian\u00e7as de 30 kgf a rede suporta? <\/b><\/span><\/span><\/span>(suponha que o \u00e2ngulo n\u00e3o mude).<\/b><\/span><\/span><\/span><\/p>\n

10-(Cesgranrio)<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

Um <\/b><\/span><\/span><\/span>corpo de peso P <\/b><\/span><\/span><\/span>encontra-se em <\/b><\/span><\/span><\/span>equil\u00edbrio,<\/b><\/span><\/span><\/span> devido \u00e0 <\/b><\/span><\/span><\/span>a\u00e7\u00e3o da for\u00e7a F, <\/b><\/span><\/span><\/span>como indica a <\/b><\/span><\/span><\/span>figura. <\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

Os <\/b><\/span><\/span><\/span>pontos A, B e C <\/b><\/span><\/span><\/span>s\u00e3o os <\/b><\/span><\/span><\/span>pontos de contato entre os fios e a superf\u00edcie.<\/b><\/span><\/span><\/span> <\/b><\/p>\n

A <\/b><\/span><\/span><\/span>for\u00e7a que a superf\u00edcie<\/b><\/span><\/span><\/span> exerce <\/b><\/span><\/span><\/span>sobre<\/b><\/span><\/span><\/span> os fios <\/b><\/span><\/span><\/span>nos pontos A, B e C s\u00e3o, <\/b><\/span><\/span><\/span>respectivamente:<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

11-(UNESP-SP)<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

Duas <\/b><\/span><\/span><\/span>esferas homog\u00eaneas, de raios R<\/b><\/span><\/span><\/span>1<\/b><\/span><\/span><\/sub><\/span>\u00a0e R<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span>\u00a0e massas m<\/b><\/span><\/span><\/span>1<\/b><\/span><\/span><\/sub><\/span>\u00a0e m<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span>, <\/b><\/span><\/span><\/span>foram <\/b><\/span><\/span><\/span>fixadas uma \u00e0 outra <\/b><\/span><\/span><\/span>de modo a <\/b><\/span><\/span><\/span>formar um sistema r\u00edgido, <\/b><\/span><\/span><\/span>indicado na <\/b><\/span><\/span><\/span>figura.<\/b><\/span><\/span><\/span>\"\"<\/p>\n

Sendo <\/b><\/span><\/span><\/span>R<\/b><\/span><\/span><\/span>1 <\/b><\/span><\/span><\/sub><\/span>= 2R<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span>\u00a0<\/b><\/span><\/span><\/span>e <\/b><\/span><\/span><\/span>m<\/b><\/span><\/span><\/span>1 <\/b><\/span><\/span><\/sub><\/span>= m<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span>\/2, <\/b><\/span><\/span><\/span>o <\/b><\/span><\/span><\/span>centro do sistema <\/b><\/span><\/span><\/span>assim <\/b><\/span><\/span><\/span>constitu\u00eddo<\/b><\/span><\/span><\/span> encontra-se:<\/b><\/span><\/span><\/span><\/p>\n

a) <\/b><\/span><\/span><\/span>no <\/b><\/span><\/span><\/span>centro<\/b><\/span><\/span><\/span> da <\/b><\/span><\/span><\/span>esfera maior.\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 <\/b><\/span><\/span><\/span><\/p>\n

b) <\/b><\/span><\/span><\/span>no <\/b><\/span><\/span><\/span>centro<\/b><\/span><\/span><\/span> da <\/b><\/span><\/span><\/span>esfera menor.\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 <\/b><\/span><\/span><\/span><\/p>\n

c) <\/b><\/span><\/span><\/span>no <\/b><\/span><\/span><\/span>ponto de fixa\u00e7\u00e3o <\/b><\/span><\/span><\/span>das esferas.<\/b><\/span><\/span><\/span><\/p>\n

d) <\/b><\/span><\/span><\/span>a <\/b><\/span><\/span><\/span>meia dist\u00e2ncia <\/b><\/span><\/span><\/span>entre o <\/b><\/span><\/span><\/span>centro O<\/b><\/span><\/span><\/span>1<\/b><\/span><\/span><\/sub><\/span>\u00a0e o ponto de fixa\u00e7\u00e3o<\/b><\/span><\/span><\/span>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 <\/b><\/span><\/span><\/span><\/p>\n

e) <\/b><\/span><\/span><\/span>a <\/b><\/span><\/span><\/span>meia dist\u00e2ncia <\/b><\/span><\/span><\/span>entre o <\/b><\/span><\/span><\/span>centro O<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span>\u00a0e o ponto de fixa\u00e7\u00e3o.<\/b><\/span><\/span><\/span><\/p>\n

12-(UFC-CE)<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

Cada um <\/b><\/span><\/span><\/span>dos <\/b><\/span><\/span><\/span>quadrados mostrados na figura <\/b><\/span><\/span><\/span>a seguir <\/b><\/span><\/span><\/span>tem lado b e massa uniformemente distribu\u00edda.<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

Determine as <\/b><\/span><\/span><\/span>coordenadas (x , y) do centro de massa <\/b><\/span><\/span><\/span>do <\/b><\/span><\/span><\/span>sistema formado pelos quadrados.<\/b><\/span><\/span><\/span><\/p>\n

13-(ITA\u2013SP)<\/b><\/span><\/span><\/span> <\/b>\u00c9 dado um <\/b><\/span><\/span><\/span>peda\u00e7o de cartolina com a forma de um sapinho, <\/b><\/span><\/span><\/span>cujo <\/b><\/span><\/span><\/span>centro de gravidade situa-se no seu pr\u00f3prio corpo. <\/b><\/span><\/span><\/span><\/p>\n

A seguir, com o <\/b><\/span><\/span><\/span>auxilio de massa de modelagem, fixamos uma moeda de 10 centavos <\/b><\/span><\/span><\/span>em cada uma das <\/b><\/span><\/span><\/span>patas dianteiras do sapinho. <\/b><\/span><\/span><\/span><\/p>\n

Apoiando-se o <\/b><\/span><\/span><\/span>nariz do sapinho na extremidade de um l\u00e1pis, <\/b><\/span><\/span><\/span>ele <\/b><\/span><\/span><\/span>permanece em equil\u00edbrio.<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

Nessas condi\u00e7\u00f5es, <\/b><\/span><\/span><\/span>pode-se afirmar que o sapinho com as moedas permanece em equil\u00edbrio est\u00e1vel porque o centro de gravidade do sistema:<\/b><\/span><\/span><\/span><\/p>\n

a) <\/b><\/span><\/span><\/span>Continua no <\/b><\/span><\/span><\/span>corpo do sapinho.\u00a0\u00a0\u00a0\u00a0\u00a0 <\/b><\/span><\/span><\/span><\/p>\n

b) <\/b><\/span><\/span><\/span>Situa-se no <\/b><\/span><\/span><\/span>ponto m\u00e9dio entre seus olhos.\u00a0\u00a0\u00a0\u00a0\u00a0 <\/b><\/span><\/span><\/span><\/p>\n

c) <\/b><\/span><\/span><\/span>Situa-se no <\/b><\/span><\/span><\/span>nariz do sapinho.<\/b><\/span><\/span><\/span><\/p>\n

d) <\/b><\/span><\/span><\/span>Situa-se <\/b><\/span><\/span><\/span>abaixo do ponto de apoio.\u00a0\u00a0\u00a0\u00a0\u00a0 <\/b><\/span><\/span><\/span><\/p>\n

e) <\/b><\/span><\/span><\/span>Situa-se no <\/b><\/span><\/span><\/span>ponto m\u00e9dio entre as patas traseiras<\/b><\/span><\/span><\/span><\/p>\n

14-(UNESP-SP)<\/b><\/span><\/span><\/span> <\/b><\/p>\n

\"\"<\/p>\n

Justifique por que uma pessoa, <\/b><\/span><\/span><\/span>sentada conforme a figura, <\/b><\/span><\/span><\/span>mantendo o tronco e t\u00edbias na vertical<\/b><\/span><\/span><\/span>\u00a0e <\/b><\/span><\/span><\/span>os p\u00e9s no piso, n\u00e3o consegue se levantar por esfor\u00e7o pr\u00f3prio. <\/b><\/span><\/span><\/span><\/p>\n

Se <\/b><\/span><\/span><\/span>julgar necess\u00e1rio<\/b><\/span><\/span><\/span>, <\/b><\/span><\/span><\/span>fa\u00e7a<\/b><\/span><\/span><\/span> um <\/b><\/span><\/span><\/span>esquema para auxiliar sua explica\u00e7\u00e3o.<\/b><\/span><\/span><\/span><\/p>\n

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

15-(ITA-SP)<\/b><\/span><\/span><\/span> Tr\u00eas blocos c\u00fabicos, id\u00eanticos de aresta <\/b><\/span><\/span><\/span>a<\/b><\/span><\/span><\/span>,<\/b><\/span><\/span><\/span> est\u00e3o <\/b><\/span><\/span><\/span>empilhados <\/b><\/span><\/span><\/span>conforme mostra a <\/b><\/span><\/span><\/span>figura. <\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

Qual \u00e9 <\/b><\/span><\/span><\/span>a m\u00e1xima dist\u00e2ncia x para que ainda se tenha equil\u00edbrio?<\/b><\/span><\/span><\/span><\/p>\n

16-Unicamp-SP)<\/b><\/span><\/span><\/span> <\/b><\/p>\n

\"\"<\/p>\n

Um <\/b><\/span><\/span><\/span>cigarro sem filtro, de 80 mm, <\/b><\/span><\/span><\/span>foi <\/b><\/span><\/span><\/span>aceso e apoiado num cinzeiro,<\/b><\/span><\/span><\/span> como mostra a <\/b><\/span><\/span><\/span>figura.<\/b><\/span><\/span><\/span> Durante <\/b><\/span><\/span><\/span>quanto tempo <\/b><\/span><\/span><\/span>o <\/b><\/span><\/span><\/span>cigarro ficar\u00e1 sobre o cinzeiro? <\/b><\/span><\/span><\/span>Considere que a <\/b><\/span><\/span><\/span>queima se d\u00e1 \u00e0 raz\u00e3o de 5 mm por minuto e que a cinza sempre se desprende do cigarro.<\/b><\/span><\/span><\/span><\/p>\n

17-(UFPR-PR)<\/b><\/span><\/span><\/span>\u00a0 Quatro blocos homog\u00eaneos e id\u00eanticos de massa m, comprimento L = 20 cm <\/b><\/span><\/span><\/span>e <\/b><\/span><\/span><\/span>espessura E = 8 cm est\u00e3o empilhados conforme mostra a figura. <\/b><\/span><\/span><\/span> <\/b>\"\"<\/p>\n

Considere que o <\/b><\/span><\/span><\/span>eixo y coincide com a parede localizada \u00e0 esquerda dos blocos, <\/b><\/span><\/span><\/span>que o <\/b><\/span><\/span><\/span>eixo x coincide com a superf\u00edcie horizontal sobre a qual os blocos se encontram <\/b><\/span><\/span><\/span>e que a <\/b><\/span><\/span><\/span>intersec\u00e7\u00e3o desses eixos define a origem O. <\/b><\/span><\/span><\/span><\/p>\n

Com base nos <\/b><\/span><\/span><\/span>dados da figura e do enunciado,<\/b><\/span><\/span><\/span> calcule as <\/b><\/span><\/span><\/span>coordenadas X e Y da posi\u00e7\u00e3o do centro de massa do conjunto de blocos.<\/b><\/span><\/span><\/span><\/p>\n

18-(UNICAMP-SP)<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

19-(UERJ-RJ)<\/b><\/span><\/span><\/span> <\/b>A <\/b><\/span><\/span><\/span>figura mostra um homem de massa igual a 100 kg, <\/b><\/span><\/span><\/span>pr\u00f3ximo a um <\/b><\/span><\/span><\/span>trilho de ferro AB, <\/b><\/span><\/span><\/span>de <\/b><\/span><\/span><\/span>comprimento e massa respectivamente iguais a 10m e 350 kg.<\/b><\/span><\/span><\/span>\"\"<\/p>\n

O trilho <\/b><\/span><\/span><\/span>encontra-se em equil\u00edbrio est\u00e1tico, <\/b><\/span><\/span><\/span>com <\/b><\/span><\/span><\/span>60% do seu comprimento total apoiados sobre a laje de uma constru\u00e7\u00e3o.<\/b><\/span><\/span><\/span><\/p>\n

Estime<\/b><\/span><\/span><\/span> a <\/b><\/span><\/span><\/span>dist\u00e2ncia m\u00e1xima <\/b><\/span><\/span><\/span>que o <\/b><\/span><\/span><\/span>homem pode se deslocar sobre o trilho, <\/b><\/span><\/span><\/span>a <\/b><\/span><\/span><\/span>partir do ponto P<\/b><\/span><\/span><\/span>, no <\/b><\/span><\/span><\/span>sentido da extremidade\u00a0B, mantendo-o em equil\u00edbrio.<\/b><\/span><\/span><\/span><\/p>\n

20-(MACKENZIE-SP)<\/b><\/span><\/span><\/span> Um “<\/b><\/span><\/span><\/span>designer” projeta um m\u00f3bile <\/b><\/span><\/span><\/span>usando <\/b><\/span><\/span><\/span>tr\u00eas hastes r\u00edgidas de pesos desprez\u00edveis<\/b><\/span><\/span><\/span>, <\/b><\/span><\/span><\/span>interligadas por fios ideais, e quatro bonequinhos, conforme a figura<\/b><\/span><\/span><\/span>.<\/b><\/span><\/span><\/span>\"\"<\/p>\n

Cada haste <\/b><\/span><\/span><\/span>tem <\/b><\/span><\/span><\/span>15cm de comprimento. <\/b><\/span><\/span><\/span>Para que o <\/b><\/span><\/span><\/span>conjunto permane\u00e7a em equil\u00edbrio,<\/b><\/span><\/span><\/span> com as <\/b><\/span><\/span><\/span>hastes na horizontal, <\/b><\/span><\/span><\/span>a <\/b><\/span><\/span><\/span>massa do bonequinho X <\/b><\/span><\/span><\/span>dever\u00e1 ser:<\/b><\/span><\/span><\/span><\/p>\n

a) <\/b><\/span><\/span><\/span>360g\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0<\/b><\/span><\/span><\/span><\/p>\n

b) <\/b><\/span><\/span><\/span>240g\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 <\/b><\/span><\/span><\/span><\/p>\n

c) <\/b><\/span><\/span><\/span>180g\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 <\/b><\/span><\/span><\/span><\/p>\n

d) <\/b><\/span><\/span><\/span>30g\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 <\/b><\/span><\/span><\/span><\/p>\n

e) <\/b><\/span><\/span><\/span>20g<\/b><\/span><\/span><\/span><\/p>\n

21-(ITA-SP)<\/b><\/span><\/span><\/span> <\/b><\/p>\n

\"\"<\/p>\n

A <\/b><\/span><\/span><\/span>figura <\/b><\/span><\/span><\/span>mostra uma <\/b><\/span><\/span><\/span>barra de 50 cm de comprimento <\/b><\/span><\/span><\/span>e <\/b><\/span><\/span><\/span>massa desprez\u00edvel,<\/b><\/span><\/span><\/span> suspensa por uma <\/b><\/span><\/span><\/span>corda OQ, <\/b><\/span><\/span><\/span>sustentando <\/b><\/span><\/span><\/span>um peso de 3000 N no ponto indicado<\/b><\/span><\/span><\/span>. <\/b><\/span><\/span><\/span><\/p>\n

Sabendo que a <\/b><\/span><\/span><\/span>barra se ap\u00f3ia sem atrito nas paredes do v\u00e3o, <\/b><\/span><\/span><\/span>a <\/b><\/span><\/span><\/span>raz\u00e3o entre a tens\u00e3o na corda <\/b><\/span><\/span><\/span>e a <\/b><\/span><\/span><\/span>rea\u00e7\u00e3o na parede no ponto S, no equil\u00edbrio est\u00e1tico, <\/b><\/span><\/span><\/span>\u00e9 igual a<\/b><\/span><\/span><\/span><\/p>\n

a) <\/b><\/span><\/span><\/span>1,5\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0<\/b><\/span><\/span><\/span><\/p>\n

b) <\/b><\/span><\/span><\/span>3,0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 <\/b><\/span><\/span><\/span><\/p>\n

c) <\/b><\/span><\/span><\/span>2,0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0<\/b><\/span><\/span><\/span><\/p>\n

d) <\/b><\/span><\/span><\/span>1,0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0<\/b><\/span><\/span><\/span><\/p>\n

e) <\/b><\/span><\/span><\/span>5,0<\/b><\/span><\/span><\/span><\/p>\n

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

22-(UFMG-MG)<\/b><\/span><\/span><\/span> <\/b>\u201cD\u00ea-me um ponto de apoio e eu moverei a Terra.\u201d<\/b><\/span><\/span><\/span><\/p>\n

Nessa frase, atribu\u00edda a Arquimedes, faz-se <\/b><\/span><\/span><\/span>refer\u00eancia \u00e0 possibilidade do uso de uma alavanca para levantar pesos muito grandes, exercendo-se uma for\u00e7a pequena.<\/b><\/span><\/span><\/span><\/p>\n

A gravura abaixo, intitulada <\/b><\/span><\/span><\/span>\u201cArquimedes movendo a Terra<\/b><\/span><\/span><\/span>\u201d, reproduz uma estampa de um livro de mec\u00e2nica de 1787:<\/b><\/span><\/span><\/span><\/p>\n

A massa da Terra \u00e9 de 6.10<\/b><\/span><\/span><\/span>24<\/b><\/span><\/span><\/sup><\/span>\u00a0kg.<\/b><\/span><\/span><\/span>\"\"<\/p>\n

Suponha que fossem dados a <\/b><\/span><\/span><\/span>Arquimedes um ponto de apoio e uma alavanca para ele levantar uma massa igual \u00e0 da Terra, a uma altura de 1 cm.<\/b><\/span><\/span><\/span> <\/b><\/p>\n

Considere, tamb\u00e9m, que <\/b><\/span><\/span><\/span>essa massa estivesse em uma regi\u00e3o onde a acelera\u00e7\u00e3o da gravidade fosse igual \u00e0 que existe na superf\u00edcie da Terra.<\/b><\/span><\/span><\/span><\/p>\n

\u00a0Considerando <\/b><\/span><\/span><\/span>essa situa\u00e7\u00e3o, ESTIME a raz\u00e3o que deveria haver entre as dist\u00e2ncias das extremidades dessa alavanca ao ponto de apoio.<\/b><\/span><\/span><\/span><\/p>\n

23-(UFRN-RN)<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

Do ponto de vista da <\/b><\/span><\/span><\/span>F\u00edsica,<\/b><\/span><\/span><\/span> o <\/b><\/span><\/span><\/span>sistema de freios dos carros atuais <\/b><\/span><\/span><\/span>\u00e9 formado por <\/b><\/span><\/span><\/span>uma alavanca e por uma prensa hidr\u00e1ulica. <\/b><\/span><\/span><\/span><\/p>\n

Enquanto a <\/b><\/span><\/span><\/span>alavanca tem a capacidade\u00a0 de amplia\u00e7\u00e3o da for\u00e7a aplicada por um fator igual \u00e0 raz\u00e3o direta de seus bra\u00e7os,<\/b><\/span><\/span><\/span> a <\/b><\/span><\/span><\/span>prensa hidr\u00e1ulica <\/b><\/span><\/span><\/span>amplia a <\/b><\/span><\/span><\/span>for\u00e7a da alavanca <\/b><\/span><\/span><\/span>na <\/b><\/span><\/span><\/span>raz\u00e3o direta de suas \u00e1reas. <\/b><\/span><\/span><\/span>Finalmente, a <\/b><\/span><\/span><\/span>for\u00e7a resultante aciona os freios, conforme mostrado na Figura, fazendo o ve\u00edculo parar.<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

Considere que a <\/b><\/span><\/span><\/span>alavanca tem bra\u00e7o maior,\u00a0 L, igual a 40cm e bra\u00e7o menor , l, igual a 10cm,<\/b><\/span><\/span><\/span> e a <\/b><\/span><\/span><\/span>prensa hidr\u00e1ulica apresenta \u00eambolos com \u00e1rea maior, A, oito vezes maior que a \u00e1rea menor, a. <\/b><\/span><\/span><\/span>Levando em considera\u00e7\u00e3o as <\/b><\/span><\/span><\/span>caracter\u00edsticas descritas\u00a0 acima, tal sistema de freios <\/b><\/span><\/span><\/span>\u00e9 capaz de fazer a <\/b><\/span><\/span><\/span>for\u00e7a exercida no pedal dos freios, pelo motorista<\/b><\/span><\/span><\/span>, aumentar<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

24-(UFJF-MG)<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

Os <\/b><\/span><\/span><\/span>pneus dianteiros de um autom\u00f3vel <\/b><\/span><\/span><\/span>foram <\/b><\/span><\/span><\/span>calibrados com 30\u00a0lb\/pol\u00b2 (21.10<\/b><\/span><\/span><\/span>4 <\/b><\/span><\/span><\/sup><\/span>N\/m\u00b2) <\/b><\/span><\/span><\/span>e os <\/b><\/span><\/span><\/span>pneus traseiros com 32\u00a0lb\/pol\u00b2 (22.10<\/b><\/span><\/span><\/span>4<\/b><\/span><\/span><\/sup><\/span>N\/m\u00b2). <\/b><\/span><\/span><\/span>\"\"<\/p>\n

A <\/b><\/span><\/span><\/span>\u00e1rea de contato dos pneus com o solo \u00e9 cerca de 110 cm\u00b2 em cada um deles. <\/b><\/span><\/span><\/span><\/p>\n

Sabe-se que a <\/b><\/span><\/span><\/span>press\u00e3o indicada pelo calibrador \u00e9 a diferen\u00e7a entre a press\u00e3o interna e a press\u00e3o atmosf\u00e9rica.<\/b><\/span><\/span><\/span><\/p>\n

a) <\/b><\/span><\/span><\/span>\u00c9 poss\u00edvel <\/b><\/span><\/span><\/span>estimar o peso de um autom\u00f3vel <\/b><\/span><\/span><\/span>conhecendo a <\/b><\/span><\/span><\/span>press\u00e3o dos pneus e a \u00e1rea de contato dos mesmos com o solo? Justifique por qu\u00ea.<\/b><\/span><\/span><\/span><\/p>\n

b) <\/b><\/span><\/span><\/span>Calcule o <\/b><\/span><\/span><\/span>peso aproximado do autom\u00f3vel do exemplo citado.<\/b><\/span><\/span><\/span><\/p>\n

25-(ENEM-MEC)<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

\"\"<\/p>\n

O <\/b><\/span><\/span><\/span>mecanismo que permite articular<\/b><\/span><\/span><\/span> uma <\/b><\/span><\/span><\/span>porta<\/b><\/span><\/span><\/span> (de um m\u00f3vel ou de acesso) \u00e9 a <\/b><\/span><\/span><\/span>dobradi\u00e7a. <\/b><\/span><\/span><\/span>Normalmente, <\/b><\/span><\/span><\/span>s\u00e3o necess\u00e1rias<\/b><\/span><\/span><\/span> <\/b>duas ou mais dobradi\u00e7as para que a porta seja fixada no m\u00f3vel ou no portal, <\/b><\/span><\/span><\/span>permanecendo em <\/b><\/span><\/span><\/span>equil\u00edbrio e podendo ser articulada com facilidade<\/b><\/span><\/span><\/span>.<\/b><\/span><\/span><\/span><\/p>\n

No plano, o <\/b><\/span><\/span><\/span>diagrama vetorial das for\u00e7as que as dobradi\u00e7as exercem na porta est\u00e1 representado em<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

26-(ESCOLA NAVAL)<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

A <\/b><\/span><\/span><\/span>viga inclinada de\u00a060<\/b><\/span><\/span><\/span>o<\/b><\/span><\/span><\/sup><\/span>\u00a0mostrada na figura <\/b><\/span><\/span><\/span>repousa sobre dois apoios\u00a0A\u00a0e\u00a0D.<\/b><\/span><\/span><\/span> <\/b><\/p>\n

Nos <\/b><\/span><\/span><\/span>pontos\u00a0C\u00a0e\u00a0E, <\/b><\/span><\/span><\/span>dois <\/b><\/span><\/span><\/span>blocos<\/b><\/span><\/span><\/span> de<\/b><\/span><\/span><\/span>\"\"<\/p>\n

massa\u00a08,00kg\u00a0est\u00e3o pendurados por meio de um fio ideal. <\/b><\/span><\/span><\/span><\/p>\n

Uma <\/b><\/span><\/span><\/span>for\u00e7a de\u00a0F=30N\u00a0traciona um fio ideal preso \u00e0 viga no ponto\u00a0B.<\/b><\/span><\/span><\/span> <\/b><\/p>\n

Desprezando o <\/b><\/span><\/span><\/span>peso da viga e o atrito no apoio\u00a0D, <\/b><\/span><\/span><\/span>a <\/b><\/span><\/span><\/span>rea\u00e7\u00e3o normal que o apoio\u00a0D\u00a0exerce na viga, <\/b><\/span><\/span><\/span>em <\/b><\/span><\/span><\/span>newtons,<\/b><\/span><\/span><\/span> \u00e9 igual a
\n<\/b><\/span><\/span><\/span>a) <\/b><\/span><\/span><\/span>30,0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0<\/b><\/span><\/span><\/span><\/p>\n

b) <\/b><\/span><\/span><\/span>50,0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0<\/b><\/span><\/span><\/span><\/p>\n

c) <\/b><\/span><\/span><\/span>70,0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0<\/b><\/span><\/span><\/span><\/p>\n

d) <\/b><\/span><\/span><\/span>90,0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0<\/b><\/span><\/span><\/span><\/p>\n

e) <\/b><\/span><\/span><\/span>110<\/b><\/span><\/span><\/span><\/p>\n

27-(ESCOLA NAVAL)<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

Uma <\/b><\/span><\/span><\/span>balan\u00e7a encontra-se equilibrada <\/b><\/span><\/span><\/span>tendo, <\/b><\/span><\/span><\/span>sobre seu prato direito, um recipiente contendo inicialmente apenas \u00e1gua. <\/b><\/span><\/span><\/span><\/p>\n

Um <\/b><\/span><\/span><\/span>cubo s\u00f3lido e uniforme, de volume 5cm<\/b><\/span><\/span><\/span>3<\/b><\/span><\/span><\/sup><\/span>, peso 0,2N <\/b><\/span><\/span><\/span>e <\/b><\/span><\/span><\/span>pendurado por um fio fino \u00e9, ent\u00e3o, lentamente mergulhado na \u00e1gua at\u00e9 que fique totalmente submerso. <\/b><\/span><\/span><\/span>Sabendo que o <\/b><\/span><\/span><\/span>cubo n\u00e3o toca o fundo do recipiente , <\/b><\/span><\/span><\/span>a <\/b><\/span><\/span><\/span>balan\u00e7a estar\u00e1 equilibrada <\/b><\/span><\/span><\/span>se for acrescentado <\/b><\/span><\/span><\/span>um contrapeso, em newtons, <\/b><\/span><\/span><\/span>igual a<\/b><\/span><\/span><\/span>\"\"<\/p>\n

Dados: <\/b><\/span><\/span><\/span>g = <\/b><\/span><\/span><\/span>10m\/s<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sup><\/span>; <\/b><\/span><\/span><\/span>massa espec\u00edfica da \u00e1gua = <\/b><\/span><\/span><\/span>1 g\/cm<\/b><\/span><\/span><\/span>3<\/b><\/span><\/span><\/sup><\/span>.<\/b><\/span><\/span><\/span><\/p>\n

a) <\/b><\/span><\/span><\/span>zero, pois a <\/b><\/span><\/span><\/span>balan\u00e7a se mant\u00e9m equilibrada.<\/b><\/span><\/span><\/span>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0<\/b><\/span><\/span><\/span><\/p>\n

b) <\/b><\/span><\/span><\/span>0,50, <\/b><\/span><\/span><\/span>colocado sobre o prato direito.<\/b><\/span><\/span><\/span><\/p>\n

c) <\/b><\/span><\/span><\/span>0,20. <\/b><\/span><\/span><\/span>colocado sobre o prato esquerdo.<\/b><\/span><\/span><\/span>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0<\/b><\/span><\/span><\/span><\/p>\n

D) <\/b><\/span><\/span><\/span>0,15, <\/b><\/span><\/span><\/span>colocado sobre o prato direito.<\/b><\/span><\/span><\/span><\/p>\n

e) <\/b><\/span><\/span><\/span>0,050, <\/b><\/span><\/span><\/span>colocado sobre o prato esquerdo.<\/b><\/span><\/span><\/span><\/p>\n

28-(ACAFE-SC)<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

Um <\/b><\/span><\/span><\/span>candidato, passando por uma rodovia, <\/b><\/span><\/span><\/span>observa algo, no m\u00ednimo, inusitado: uma <\/b><\/span><\/span><\/span>placa de outdoor sustentada por dois de seus quatro pilares.<\/b><\/span><\/span><\/span><\/p>\n

Para <\/b><\/span><\/span><\/span>exercitar seus conhecimentos de f\u00edsic<\/b><\/span><\/span><\/span>a imaginou a placa de outdoor <\/b><\/span><\/span><\/span>homog\u00eanea de massa\u00a0\u00a0100 kg, como mostra a figura.<\/b><\/span><\/span><\/span><\/p>\n

Despreze <\/b><\/span><\/span><\/span>os atritos <\/b><\/span><\/span><\/span>entre a <\/b><\/span><\/span><\/span>placa e os pilares e entre a placa e os parafusos; desconsidere<\/b><\/span><\/span><\/span> tamb\u00e9m a <\/b><\/span><\/span><\/span>massa dos pilares.\u00a0\u00a0<\/b><\/span><\/span><\/span>\"\"<\/p>\n

Neste sentido, <\/b><\/span><\/span><\/span>sabendo que a placa est\u00e1 em equil\u00edbrio, <\/b><\/span><\/span><\/span>assinale a <\/b><\/span><\/span><\/span>alternativa correta <\/b><\/span><\/span><\/span>que representa o <\/b><\/span><\/span><\/span>vetor for\u00e7a aplicado pelos parafusos dos pilares (1) e (2) sobre a placa e seus m\u00f3dulos,<\/b><\/span><\/span><\/span> respectivamente. <\/b><\/span><\/span><\/span>(g = 10m\/s<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sup><\/span>).<\/b><\/span><\/span><\/span><\/p>\n

A) <\/b><\/span><\/span><\/span>\u2193 \u2212 F<\/b><\/span><\/span><\/span>1<\/b><\/span><\/span><\/sub><\/span>=50N ; \u2193 \u2212 F<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span>\u00a0=150N\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0<\/b><\/span><\/span><\/span><\/p>\n

B) <\/b><\/span><\/span><\/span>\u2191 \u2212 F<\/b><\/span><\/span><\/span>1<\/b><\/span><\/span><\/sub><\/span>\u00a0=150N ; \u2193 \u2212 F<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span>\u00a0=50N\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0<\/b><\/span><\/span><\/span><\/p>\n

C) <\/b><\/span><\/span><\/span>\u2193 \u2212 F<\/b><\/span><\/span><\/span>1<\/b><\/span><\/span><\/sub><\/span>=500N ; \u2191 \u2212 F<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span>\u00a0=1500N\u00a0<\/b><\/span><\/span><\/span><\/p>\n

D) <\/b><\/span><\/span><\/span>\u2191 \u2212 F<\/b><\/span><\/span><\/span>1<\/b><\/span><\/span><\/sub><\/span>=1500N ; \u2191 \u2212 F<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span>=500N<\/b><\/span><\/span><\/span><\/p>\n

29-(EsPCEx-SP)<\/b><\/span><\/span><\/span><\/p>\n

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

Um\u00a0<\/b><\/span><\/span><\/span>port\u00e3o maci\u00e7o e homog\u00eaneo\u00a0de\u00a01,60m de largura <\/b><\/span><\/span><\/span>e <\/b><\/span><\/span><\/span>1,80m de comprimento,\u00a0pesando 800N\u00a0<\/b><\/span><\/span><\/span>est\u00e1 <\/b><\/span><\/span><\/span>fixado em um muro por meio das\u00a0dobradi\u00e7as “A”, situada\u00a0a 0,10m\u00a0abaixo do topo do port\u00e3o, <\/b><\/span><\/span><\/span>e\u00a0<\/b><\/span><\/span><\/span>“B”,\u00a0situada a 0,10 m\u00a0de sua parte inferior. <\/b><\/span><\/span><\/span><\/p>\n

A\u00a0<\/b><\/span><\/span><\/span>dist\u00e2ncia entre as dobradi\u00e7as \u00e9 de 1,60m\u00a0<\/b><\/span><\/span><\/span>conforme o <\/b><\/span><\/span><\/span>desenho.<\/b><\/span><\/span><\/span> <\/b>\"\"<\/p>\n

Elas t\u00eam peso e dimens\u00f5es desprez\u00edveis, <\/b><\/span><\/span><\/span>e\u00a0<\/b><\/span><\/span><\/span>cada dobradi\u00e7a suporta uma for\u00e7a cujo m\u00f3dulo da componente vertical \u00e9 metade do peso do port\u00e3o.<\/b><\/span><\/span><\/span><\/p>\n

Considerando que o <\/b><\/span><\/span><\/span>port\u00e3o est\u00e1 em\u00a0equil\u00edbrio, <\/b><\/span><\/span><\/span>e que o seu\u00a0<\/b><\/span><\/span><\/span>centro de gravidade\u00a0est\u00e1 localizado <\/b><\/span><\/span><\/span>em\u00a0<\/b><\/span><\/span><\/span>seu centro geom\u00e9trico, <\/b><\/span><\/span><\/span>o <\/b><\/span><\/span><\/span>m\u00f3dulo da componente horizontal da for\u00e7a em cada dobradi\u00e7a “A” e “B”<\/b><\/span><\/span><\/span><\/p>\n

vale, respectivamente:<\/b><\/span><\/span><\/span><\/p>\n

a) <\/b><\/span><\/span><\/span>130 N e 135 N <\/b><\/span><\/span><\/span><\/p>\n

b) <\/b><\/span><\/span><\/span>135 N e 135 N <\/b><\/span><\/span><\/span><\/p>\n

c) <\/b><\/span><\/span><\/span>400 N e 400 N <\/b><\/span><\/span><\/span><\/p>\n

d) <\/b><\/span><\/span><\/span>450 N e 450 N <\/b><\/span><\/span><\/span><\/p>\n

e) <\/b><\/span><\/span><\/span>600 N e 65ON<\/b><\/span><\/span><\/span><\/p>\n

30-(EsPCEx-SP)<\/b><\/span><\/span><\/span><\/p>\n

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

Um <\/b><\/span><\/span><\/span>trabalhador da constru\u00e7\u00e3o civil <\/b><\/span><\/span><\/span>tem\u00a0<\/b><\/span><\/span><\/span>massa de 70kg\u00a0e utiliza uma polia<\/b><\/span><\/span><\/span> e uma <\/b><\/span><\/span><\/span>corda ideais <\/b><\/span><\/span><\/span>e <\/b><\/span><\/span><\/span>sem<\/b><\/span><\/span><\/span><\/p>\n

atrito para transportar\u00a0telhas do solo at\u00e9 a cobertura de uma resid\u00eancia <\/b><\/span><\/span><\/span>em obras, conforme <\/b><\/span><\/span><\/span>desenho.<\/b><\/span><\/span><\/span><\/p>\n

O\u00a0<\/b><\/span><\/span><\/span>coeficiente de atrito est\u00e1tico\u00a0<\/b><\/span><\/span><\/span>entre a <\/b><\/span><\/span><\/span>sola do sapato do trabalhador e o ch\u00e3o <\/b><\/span><\/span><\/span>de concreto \u00e9\u00a0<\/b><\/span><\/span><\/span>\u03bc<\/b><\/span><\/span><\/span>e <\/b><\/span><\/span><\/sub><\/span>= 1,0<\/b><\/span><\/span><\/span>\"\"<\/p>\n

e a\u00a0<\/b><\/span><\/span><\/span>massa de cada telha \u00e9 de 2kg.<\/b><\/span><\/span><\/span><\/p>\n

O\u00a0<\/b><\/span><\/span><\/span>n\u00famero m\u00e1ximo\u00a0de telhas <\/b><\/span><\/span><\/span>que podem ser\u00a0<\/b><\/span><\/span><\/span>sustentadas em repouso,<\/b><\/span><\/span><\/span> acima do solo,\u00a0<\/b><\/span><\/span><\/span>sem que o trabalhador deslize, <\/b><\/span><\/span><\/span>permanecendo\u00a0<\/b><\/span><\/span><\/span>est\u00e1tico no solo, para um\u00a0\u00e2ngulo \u03b8 entre a corda e a horizontal,<\/b><\/span><\/span><\/span> \u00e9:<\/b><\/span><\/span><\/span><\/p>\n

Dados: <\/b><\/span><\/span><\/span>Acelera\u00e7\u00e3o da gravidade:\u00a0<\/b><\/span><\/span><\/span>g = 10 m\/s<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sup><\/span>, cos \u03b8 = 0,8 e sen \u03b8 = 0,6.<\/b><\/span><\/span><\/span><\/p>\n

a) <\/b><\/span><\/span><\/span>30 <\/b><\/span><\/span><\/span><\/p>\n

b) <\/b><\/span><\/span><\/span>25 <\/b><\/span><\/span><\/span><\/p>\n

c) <\/b><\/span><\/span><\/span>20 <\/b><\/span><\/span><\/span><\/p>\n

d) <\/b><\/span><\/span><\/span>16 <\/b><\/span><\/span><\/span><\/p>\n

e) <\/b><\/span><\/span><\/span>10<\/b><\/span><\/span><\/span><\/p>\n

31-(UNCISAL-AL)<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

A\u00a0<\/b><\/span><\/span><\/span>aferi\u00e7\u00e3o da massa\u00a0de uma pessoa pode ser realizada por meio de uma\u00a0balan\u00e7a digital de banheiro. <\/b><\/span><\/span><\/span>Para tanto, \u00e9 <\/b><\/span><\/span><\/span>necess\u00e1rio que seja posicionado os dois p\u00e9s sobre a plataforma da balan\u00e7a<\/b><\/span><\/span><\/span> e aguardar que <\/b><\/span><\/span><\/span>entre em equil\u00edbrio, sendo, posteriormente, exibido o valor aferido em um visor de LCD. <\/b><\/span><\/span><\/span><\/p>\n

No manual, consta a <\/b><\/span><\/span><\/span>recomenda\u00e7\u00e3o:<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>\u201c N\u00e3o utilizar a balan\u00e7a em superf\u00edcies inclinadas\u201d.<\/b><\/span><\/span><\/span>\"\"<\/p>\n

Que\u00a0<\/b><\/span><\/span><\/span>erros de medida podem ocorrer se esta recomenda\u00e7\u00e3o n\u00e3o for atendida?<\/b><\/span><\/span><\/span><\/p>\n

A)\u00a0<\/b><\/span><\/span><\/span>O <\/b><\/span><\/span><\/span>valor aferido ser\u00e1 menor que o valor real,<\/b><\/span><\/span><\/span> pois a componente do peso na dire\u00e7\u00e3o paralela \u00e0 superf\u00edcie da balan\u00e7a ser\u00e1 menor, reduzindo a for\u00e7a de rea\u00e7\u00e3o da balan\u00e7a.<\/b><\/span><\/span><\/span><\/p>\n

B)\u00a0<\/b><\/span><\/span><\/span>O <\/b><\/span><\/span><\/span>valor aferido ser\u00e1 menor que o valor real, <\/b><\/span><\/span><\/span>pois a componente da for\u00e7a de rea\u00e7\u00e3o da balan\u00e7a na dire\u00e7\u00e3o paralela \u00e0 sua superf\u00edcie ser\u00e1 reduzida.<\/b><\/span><\/span><\/span><\/p>\n

C)\u00a0<\/b><\/span><\/span><\/span>O <\/b><\/span><\/span><\/span>valor aferido ser\u00e1 maior que o valor real, <\/b><\/span><\/span><\/span>pois a componente do peso na dire\u00e7\u00e3o paralela \u00e0<\/b><\/span><\/span><\/span><\/p>\n

superf\u00edcie da balan\u00e7a ser\u00e1 maior, aumentando a for\u00e7a de rea\u00e7\u00e3o da balan\u00e7a.<\/b><\/span><\/span><\/span><\/p>\n

D)\u00a0<\/b><\/span><\/span><\/span>O <\/b><\/span><\/span><\/span>valor aferido ser\u00e1 menor que o valor real, <\/b><\/span><\/span><\/span>pois a componente do peso na dire\u00e7\u00e3o perpendicular \u00e0 superf\u00edcie da balan\u00e7a ser\u00e1 menor, reduzindo a for\u00e7a de rea\u00e7\u00e3o da balan\u00e7a.<\/b><\/span><\/span><\/span><\/p>\n

E)\u00a0O valor aferido ser\u00e1 maior que o valor real, <\/b><\/span><\/span><\/span>pois a componente da for\u00e7a de rea\u00e7\u00e3o da balan\u00e7a na dire\u00e7\u00e3o perpendicular \u00e0 sua superf\u00edcie ser\u00e1 maior.<\/b><\/span><\/span><\/span><\/p>\n

 <\/p>\n

Confira as resolu\u00e7\u00f5es comentadas<\/span><\/a><\/h3>\n","protected":false},"excerpt":{"rendered":"

Est\u00e1tica Como esse conte\u00fado envolve muita teoria, em caso de d\u00favidas voc\u00ea pode encontr\u00e1-la em fisicaevestibular.com.br \u2013 Mec\u00e2nica \u2013 Est\u00e1tica) 01- (UNIFOR-CE) \u00a0Com 6 peda\u00e7os iguais de corda e tr\u00eas corpos de mesma massa e mesmo formato, um estudante fez as montagens representadas abaixo. Nos peda\u00e7os de corda a intensidade da for\u00e7a de tra\u00e7\u00e3o \u00e9 (A) a mesma nas montagens<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":2508,"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-2618","page","type-page","status-publish","hentry"],"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/pages\/2618","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=2618"}],"version-history":[{"count":2,"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/pages\/2618\/revisions"}],"predecessor-version":[{"id":2623,"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/pages\/2618\/revisions\/2623"}],"up":[{"embeddable":true,"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/pages\/2508"}],"wp:attachment":[{"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/media?parent=2618"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}