Questões - AFA | Gabarito e resoluções

(AFA - 2013) Uma pequena esfera de massa m mantida comprimindo uma mola ideal de constante elstica k de tal forma que a sua deformao vale x. Ao ser disparada, essa esfera percorre a superfcie horizontal at passar pelo ponto A subindo por um plano inclinado de 45 e, ao final dele, no ponto B, lanada, atingindo uma altura mxima H e caindo no ponto C distante 3h do ponto A, conforme figura abaixo. Considerando a acelerao da gravidade igual a g e desprezando quaisquer formas de atrito, pode-se afirmar que a deformao x dada por

(AFA - 2013) Em um local onde a acelerao da gravidade vale g, uma partcula move-se sem atrito sobre uma pista circular que, por sua vez, possui uma inclinao . Essa partcula est presa a um poste central, por meio de um fio ideal de comprimentoque, atravs de uma articulao, pode girar livremente em torno do poste. O fio mantido paralelo superfcie da pista, conforme figura abaixo. Ao girar com uma determinada velocidade constante, a partcula fica flutuando sobre a superfcie inclinada da pista, ou seja, a partcula fica na iminncia de perder o contato com a pista e, alm disso, descreve uma trajetria circular com centro em C, tambm indicado na figura. Nessas condies, a velocidade linear da partcula deve ser igual a

(AFA - 2013) Uma mquina trmica funciona fazendo com que 5 mols de um gs ideal percorra o ciclo ABCDA representado na figura. Sabendo-se que a temperatura em A 227 C, que os calores especficos molares do gs, a volume constante e a presso constante, valem, respectivamente, 3/2R e 5/2 R e que R vale aproximadamente 8 J/mol K, o rendimento dessa mquina, em porcentagem, est mais prximo de

(AFA - 2013) A figura abaixo mostra uma face de um arranjo cbico, montado com duas partes geometricamente iguais. A parte 1 totalmente preenchida com um lquido de ndice de refrao n1 e a parte 2 um bloco macio de um material transparente com ndice de refrao n2. Neste arranjo, um raio de luz monocromtico, saindo do ponto P, chega ao ponto C sem sofrer desvio de sua direo inicial. Retirando-se o lquido n1 e preenchendo-se completamente a parte 1 com um outro lquido de ndice de refrao n3, tem-se que o mesmo raio, saindo do ponto P, chega integralmente ao ponto D. Considere que todos os meios sejam homogneos, transparentes e isotrpicos, e que a interface entre eles forme um diptro perfeitamente plano. Nessas condies, correto afirmar que o ndice de refrao n3 pode ser igual a

(AFA - 2013) Ondas sonoras so produzidas por duas cordas A e B prximas,vibrando em seus modos fundamentais, de tal forma que se percebe x batimentos sonoros porsegundo como resultado da superposio dessas ondas. As cordas possuem iguaiscomprimentos e densidades lineares sempre constantes, mas so submetidas a diferentestenses.Aumentando-se lentamente a tenso na corda A, chega-se a uma condio onde a frequnciade batimento nula e ouve-se apenas uma nica onda sonora de frequncia f.Nessas condies, a razo entre a maior e a menor tenso na corda A :

(AFA - 2013) Num local onde a acelerao da gravidade constante, um corpo de massa m, com dimenses desprezveis, posto a oscilar, unido a uma mola ideal de constante elstica k , em um plano fixo e inclinado de um ngulo como mostra a figura abaixo. Nessas condies, o sistema massa-mola executa um movimento harmnico simples de perodo T. Colocando-se o mesmo sistema massa-mola para oscilar na vertical, tambm em movimento harmnico simples, o seu novo perodo passa a ser T. Nessas condies, a razo T/T

(AFA - 2013) Uma partcula de massa m e carga eltrica negativa gira em rbitacircular com velocidade escalar constante de mdulo igual a v, prxima a uma carga eltricapositiva fixa, conforme ilustra a figura abaixo. Desprezando a interao gravitacional entre as partculas e adotando a energia potencialeltrica nula quando elas esto infinitamente afastadas, correto afirmar que a energia destesistema igual a

(AFA - 2013) No circuito eltrico esquematizado abaixo, a leitura no ampermetro Ano se altera quando as chaves C1 e C2 so simultaneamente fechadas. Considerando que a fonte de tenso , o ampermetro e os fios de ligao so ideais e os resistores hmicos, o valor de R igual a:

(AFA -2013) No circuito esquematizado abaixo, C1 e C2 so capacitores de placasparalelas, a ar, sendo que C2 pode ter sua capacitncia alterada por meio da inclinao de suaarmadura A, que articulada no ponto P. Estando os capacitores completamente carregados, desliga-se a chave Ch e inclina-se aarmadura A sem deix-la aproximar muito de B. Nessas condies, a ddp nos terminais de C1e C2, respectivamente:

(AFA - 2013) Um gerador homopolar consiste de um disco metlico que posto a girarcom velocidade angular constante em um campo magntico uniforme, cuja ao extensiva atoda a rea do disco, conforme ilustrado na figura abaixo. Ao conectar, entre a borda do disco e o eixo metlico de rotao, uma lmpada L cujaresistncia eltrica tem comportamento hmico, a potncia dissipada no seu filamento, emfuno do tempo, melhor representada pelo grfico

(AFA - 2013) O eltron do tomo de hidrognio, ao passar do primeiro estadoestacionrio excitado, n = 2, para o estado fundamental, n = 1, emite um fton.Tendo em vista o diagrama da figura abaixo, que apresenta, de maneira aproximada, oscomprimentos de onda das diversas radiaes, componentes do espectro eletromagntico,pode-se concluir que o comprimento de onda desse fton emitido corresponde a uma radiaona regio do(s):

(AFA - 2013) Na regio prxima a uma bobina percorrida por corrente eltrica contnua, existe um campo de induo magntica B, simtrico ao seu eixo (eixo x), cuja magnitude diminui com o aumento do mdulo da abscissa x, como mostrado na figura abaixo. Uma partcula de carga negativa lanada em x = x0 com uma velocidade v0 formando um ngulo com o sentido positivo do eixo x. O mdulo da velocidade v descrita por essa partcula, devido somente ao desse campo magntico, em funo da posio x, melhor representado pelo grfico

(AFA - 2013) Raios X so produzidos em tubos de vcuo nos quais eltrons soacelerados por uma ddp de 4,0 104 V e, em seguida, submetidos a uma intensadesacelerao ao colidir com um alvo metlico.Assim, um valor possvel para o comprimento de onda, em angstrons, desses raios X ,

(AFA - 2013) TEXT I BRAZILIAN AIR FORCE ACADEMY AFA (Air Force Academy), located at Pirassununga, State of So Paulo, is responsible for the training of Pilots, Administrative and Aeronautics Infantry Officers for the Brazilian Air Force. The history of the Brazilian military pilots schools goes back to 1913, when theBrazilian Aviation Schoolwas founded, atCampo dos Afonsos, State of Rio de Janeiro. Its mission was to provide instruction at similar levels to those of the best European schools at the time;BlriotandFarmanaircraft, made in France, were available for the instruction of the pupils. The Great War 1914-1918, however, forced its instructors to leave and the school was closed. At that time, both theBrazilian ArmyandNavyhad their own air arms, theMilitary Aviationand theNaval Aviation. The Navy boughtCurtiss Fseaplanes in May 1916 to equip the latter, and in August of the same year, theNaval Aviation Schoolwas created. The Military Aviation, however, only activated itsMilitary Aviation Schoolafter the Great War, on 10 July 1919. Among the aircrafts used at the school, one could find theSopwith 1A2,Brguet 14A2, andSpad 7. Until the beginning of the 1940s, both schools continued with their activities.1The Brazilian Government was concerned with the air war in Europe and decided to concentrate under a single command the military aviation activities.6Thus, on 20 January 1941, the Air Ministry was created and both the Army and Navy air arms were disbanded, their personnel and equipment forming theBrazilian Air Force. On 25 March 1941, theAeronautics Schoolwas based at Campo dos Afonsos, and its students became known asAeronautics Cadetsfrom 1943 to the current days. As early as 1942, it became clear that theAeronautics Schoolwould need to be transferred to another place, offering better climate and little interference with the flight instruction of the future pilots.2The town of Pirassununga was chosen among others, and, in 1952, the first buildings construction was initiated. The transfer of the School activities to Pirassununga occurred from 1960 to 1971.3The School was redesigned as theAir Force Academyin 1969. The motto of the Academy is the Latin expression Macte Animo! Generose Puer, sic itur ad astra, extracted from the poemThebaida, by the Roman poet Tatius. It is an exhortation to the cadets, which can be translated asCourage! This is the way, oh noble youngster, to the stars. The instruction of theAeronautics Cadets, during the four-year-long course, has its activities centred in the wordsCOURAGE LOYALTY HONOUR DUTY MOTHERLAND. The future officers take courses on several subjects, including Calculus, Computer Science, Mechanics, Portuguese and English, given by civilian lecturers, Air Force instructors and supervisors. The military instruction itself is given on a daily basis, and4the Cadets are trained on different subjects, including parachuting, and sea and jungle survival. Flight instruction at the Academy with T-27 Tucano aircraft. According to the chosen specialization, the Cadet will receive specific instruction: Pilots: Instruction on precision maneuvering, aerobatics, formation flying and by instruments, with 75 flying hours on the primary/basic training aircraft T-25 Universal, beginning on the 2nd term of the 1st year and completed in the 3rd year. Advanced training is given on T-27 Tucano aircraft, with 125 flying hours. Administrative: Training on the scientific and technological modern foundations of economics and financial management, and logistics training. Aeronautics Infantry: Instruction on defense and security techniques of militaryAeronauticsinstallations, anti-aircraft measures, command of troops and firefighting teams, military laws and regulations, armament usage, military service and call-up procedures. During their leisure time, the Cadets participate on the activities of seven different clubs:Aeromodelling,Literature,Informatics,Firearms shooting,Gauchos Heritage(for those coming from the South of Brazil),Gerais ClubandSail Flying. The clubs are directed by the Cadets themselves, under supervision of Air Force officers. The Academy also houses theBrazilian Air Force Air Demonstration Squadron The Smoke Squadron. Flying as the eagles do! Adapted from http://www.rudnei.cunha.nom.br/FAB/en/afa.html Mark the option that is related to the Air Force Academy.

(AFA - 2013) TEXT I BRAZILIAN AIR FORCE ACADEMY AFA (Air Force Academy), located at Pirassununga, State of So Paulo, is responsible for the training of Pilots, Administrative and Aeronautics Infantry Officers for the Brazilian Air Force. The history of the Brazilian military pilots schools goes back to 1913, when theBrazilian Aviation Schoolwas founded, atCampo dos Afonsos, State of Rio de Janeiro. Its mission was to provide instruction at similar levels to those of the best European schools at the time;BlriotandFarmanaircraft, made in France, were available for the instruction of the pupils. The Great War 1914-1918, however, forced its instructors to leave and the school was closed. At that time, both theBrazilian ArmyandNavyhad their own air arms, theMilitary Aviationand theNaval Aviation. The Navy boughtCurtiss Fseaplanes in May 1916 to equip the latter, and in August of the same year, theNaval Aviation Schoolwas created. The Military Aviation, however, only activated itsMilitary Aviation Schoolafter the Great War, on 10 July 1919. Among the aircrafts used at the school, one could find theSopwith 1A2,Brguet 14A2, andSpad 7. Until the beginning of the 1940s, both schools continued with their activities.1The Brazilian Government was concerned with the air war in Europe and decided to concentrate under a single command the military aviation activities.6Thus, on 20 January 1941, the Air Ministry was created and both the Army and Navy air arms were disbanded, their personnel and equipment forming theBrazilian Air Force. On 25 March 1941, theAeronautics Schoolwas based at Campo dos Afonsos, and its students became known asAeronautics Cadetsfrom 1943 to the current days. As early as 1942, it became clear that theAeronautics Schoolwould need to be transferred to another place, offering better climate and little interference with the flight instruction of the future pilots.2The town of Pirassununga was chosen among others, and, in 1952, the first buildings construction was initiated. The transfer of the School activities to Pirassununga occurred from 1960 to 1971.3The School was redesigned as theAir Force Academyin 1969. The motto of the Academy is the Latin expression Macte Animo! Generose Puer, sic itur ad astra, extracted from the poemThebaida, by the Roman poet Tatius. It is an exhortation to the cadets, which can be translated asCourage! This is the way, oh noble youngster, to the stars. The instruction of theAeronautics Cadets, during the four-year-long course, has its activities centred in the wordsCOURAGE LOYALTY HONOUR DUTY MOTHERLAND. The future officers take courses on several subjects, including Calculus, Computer Science, Mechanics, Portuguese and English, given by civilian lecturers, Air Force instructors and supervisors. The military instruction itself is given on a daily basis, and4the Cadets are trained on different subjects, including parachuting, and sea and jungle survival. Flight instruction at the Academy with T-27 Tucano aircraft. According to the chosen specialization, the Cadet will receive specific instruction: Pilots: Instruction on precision maneuvering, aerobatics, formation flying and by instruments, with 75 flying hours on the primary/basic training aircraft T-25 Universal, beginning on the 2nd term of the 1st year and completed in the 3rd year. Advanced training is given on T-27 Tucano aircraft, with 125 flying hours. Administrative: Training on the scientific and technological modern foundations of economics and financial management, and logistics training. Aeronautics Infantry: Instruction on defense and security techniques of militaryAeronauticsinstallations, anti-aircraft measures, command of troops and firefighting teams, military laws and regulations, armament usage, military service and call-up procedures. During their leisure time, the Cadets participate on the activities of seven different clubs:Aeromodelling,Literature,Informatics,Firearms shooting,Gauchos Heritage(for those coming from the South of Brazil),Gerais ClubandSail Flying. The clubs are directed by the Cadets themselves, under supervision of Air Force officers. The Academy also houses theBrazilian Air Force Air Demonstration Squadron The Smoke Squadron. Flying as the eagles do! Adapted from http://www.rudnei.cunha.nom.br/FAB/en/afa.html Read the statements in order to mark only the correct ones according to the text. I. The military aviation work had to be controlled by Europe in the beginning of the 1940s because of a war. II. Because of a war, the government resolved to unify the military aviation operation under a single command. III. A single officer was chosen to concentrate the military aviation skills. IV. As the Brazilian government got worried, it was decided to join the military aviation operations due to air European war.