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Julgue os itens a seguir, acerca de escoamentos compressíveis.
No estudo de escoamentos compressíveis, um parâmetro adimensional bastante utilizado, que relaciona a velocidade do escoamento e a velocidade do som no vácuo, é denominado número de Mach.
Julgue os itens que se seguem com relação à camada-limite em escoamentos sobre superfícies externas.
Quando o gradiente de pressão no escoamento sobre uma superfície é não-nulo, um fenômeno denominado separação do escoamento, ou descolamento da camada-limite, pode ocorrer. A condição necessária para que esse fenômeno ocorra é que o gradiente de pressão seja positivo, na direção do escoamento.
Julgue os itens que se seguem com relação à camada-limite em escoamentos sobre superfícies externas.
O arrasto em corpos submersos é devido exclusivamente às forças viscosas e de pressão, sendo que a contribuição das forças viscosas é preponderante em relação à contribuição das forças de pressão.
Com relação ao escoamento incompressível paralelo sobre uma placa plana, julgue os próximos itens.
Na região do escoamento fora da camada-limite, o efeito da viscosidade é desprezível e o escoamento pode ser considerado ideal.
Assumindo que o número de Reynolds do escoamento de um fluido incompressível em determinado duto circular de 0,12 m de diâmetro seja igual a 3.167, julgue os seguintes itens.
A perda de carga total no escoamento através de dutos conectados é devida às perdas distribuídas e localizadas. Na situação considerada, caso houvesse uma conexão de redução, a perda de carga localizada nessa conexão poderia ser determinada analiticamente considerando-se o escoamento invíscido e utilizando-se a equação de Bernoulli.
Assumindo que o número de Reynolds do escoamento de um fluido incompressível em determinado duto circular de 0,12 m de diâmetro seja igual a 3.167, julgue os seguintes itens.
O número de Reynolds em um duto de 0,2 m de diâmetro, conectado ao referido duto de 0,12 m de diâmetro por meio de uma conexão de redução, é igual a 1.900.
Considerando um escoamento incompressível, bidimensional e irrotacional, julgue os itens subseqüentes.
A superposição dos escoamentos planos elementares de um dipolo e de um escoamento uniforme representa o escoamento em torno de um cilindro circular.
Considerando um escoamento incompressível, bidimensional e irrotacional, julgue os itens subseqüentes.
Nesse tipo de escoamento, a vorticidade e a circulação são nulas.
Julgue os itens a seguir, a respeito da análise diferencial dos movimentos dos fluidos.
A equação de Bernoulli pode ser obtida pela integração da equação de Euler ao longo de uma linha de corrente de um escoamento em regime permanente.
Julgue os itens a seguir, acerca dos fluidos e suas propriedades.
A vazão de ar através de um medidor Venturi pode ser determinada pelo princípio da conservação da energia mecânica, desde que o escoamento seja incompressível em regime permanente e que a diferença de pressão medida no medidor Venturi seja conhecida.
Julgue os itens a seguir, acerca dos fluidos e suas propriedades.
Quando um jato de água que sai de um bocal atinge, perpendicularmente, um disco estacionário conectado a uma célula de carga, a vazão de água pode ser determinada indiretamente, utilizando-se o princípio da continuidade e o valor da força medida pela célula de carga.
Julgue os itens a seguir, acerca dos fluidos e suas propriedades.
A lei da conservação da massa para um volume de controle em regime permanente estabelece que a diferença entre a soma de todas as vazões mássicas de saída e a soma de todas as vazões mássicas de entrada deve ser nula.
Julgue os itens a seguir, acerca dos fluidos e suas propriedades.
Para a determinação da força resultante exercida por um fluido estático em um ponto de uma superfície curva submersa, deve-se calcular as componentes tangencial e normal à superfície submersa. A componente tangencial é devida às tensões de cisalhamento no fluido e a componente normal é devida ao campo de pressão hidrostática.
Julgue os itens a seguir, acerca dos fluidos e suas propriedades.
O princípio de Arquimedes estabelece que o empuxo sobre um objeto imerso em um líquido em repouso é igual ao peso do líquido deslocado pelo objeto.
Julgue os itens a seguir, acerca dos fluidos e suas propriedades.
No escoamento em regime permanente, uma partícula fluida em movimento sobre uma linha de corrente permanecerá sobre ela.
Julgue os itens a seguir, acerca dos fluidos e suas propriedades.
Os fluidos pseudoplásticos, após sofrerem deformação, retornam parcialmente à sua forma original quando a tensão aplicada é retirada.
Julgue os itens a seguir, acerca dos fluidos e suas propriedades.
Em fluidos newtonianos, a tensão de cisalhamento é diretamente proporcional à taxa de deformação, exceto para taxas de deformação muito altas.
This text refers to items 36 through 50.
Coming changes in electrical outlets and plugs
1 Do you ever pay attention to the plug when buying
appliances? From now on, you will have to. Based
on INMETRO’s regulations, a new law already in effect makes
4 grounding mandatory. Therefore, three-prong plugs will
become commonplace, giving extra work to consumers as
early as this year.
7 The third prong provides a path to ground along
which the electric current travels. Electrical outlets will also
have three-wire receptacles that accommodate electrical\quad
10 cords with three-prong plugs. Most major appliances, such as
stoves, refrigerators, and computers, have three-prong plugs,
meaning that they are grounded. Most older homes do not
13 have three-wire receptacles. If yours does not, you should
have an electrician rewire the home to accommodate the
three-prong plugs. Although three-prong adapters (called
16 cheater plugs) can be purchased, they are not recommended
for permanent use. Also remember never to clip the third
prong off a plug to make it fit a two-hole outlet.
19 The idea behind grounding is to protect the people
who use metal encased appliances from electric shock.
The casing is connected directly to the ground prong. Thus,
22 INMETRO’s concern is solely with safety. People touching
a refrigerator, for instance, will not get any potentially fatal
shocks.
25 Changes will have been introduced gradually by
2009, so as not to cause a profound impact on the population.
Electrical outlets will already be available with the third
28 receptacle. However, this will be useless unless it is
grounded. By law, new constructions must have grounding.
As of 2010, all appliances which need the third
prong will already include it. Not all outlets need to be
31 modified. Only those which will accommodate three-prong
plugs such as those for washing machines. Old appliances
34 with round pins will continue to operate normally.
With this initiative, INMETRO expects to solve
existing problems with electrical outlets. At present, there are
37 around twelve different types on the market. It is not
uncommon to try to push the plug into an outlet without
being completely successful. If it is not totally pushed in, the
40 part that is left out becomes a great risk of accidents. With
the new standard plug such risk will be eliminated.
Appliances which will continue to operate with two-
43 prong plugs are televisions, DVDs, video games and
blenders. Those requiring the third prong are microwave
ovens, air conditioners, washing machines, and freezers.
Internet: <extra.globo.com/economia/materiais>; <www.tva.gov>; <www.istockphoto.com/file_closeu> (with adaptations).
the picture and text as reference, judge the following items.
"requiring" (L.44) can be correctly replaced by which require without any change in meaning.
This text refers to items 36 through 50.
Coming changes in electrical outlets and plugs
1 Do you ever pay attention to the plug when buying
appliances? From now on, you will have to. Based
on INMETRO’s regulations, a new law already in effect makes
4 grounding mandatory. Therefore, three-prong plugs will
become commonplace, giving extra work to consumers as
early as this year.
7 The third prong provides a path to ground along
which the electric current travels. Electrical outlets will also
have three-wire receptacles that accommodate electrical\quad
10 cords with three-prong plugs. Most major appliances, such as
stoves, refrigerators, and computers, have three-prong plugs,
meaning that they are grounded. Most older homes do not
13 have three-wire receptacles. If yours does not, you should
have an electrician rewire the home to accommodate the
three-prong plugs. Although three-prong adapters (called
16 cheater plugs) can be purchased, they are not recommended
for permanent use. Also remember never to clip the third
prong off a plug to make it fit a two-hole outlet.
19 The idea behind grounding is to protect the people
who use metal encased appliances from electric shock.
The casing is connected directly to the ground prong. Thus,
22 INMETRO’s concern is solely with safety. People touching
a refrigerator, for instance, will not get any potentially fatal
shocks.
25 Changes will have been introduced gradually by
2009, so as not to cause a profound impact on the population.
Electrical outlets will already be available with the third
28 receptacle. However, this will be useless unless it is
grounded. By law, new constructions must have grounding.
As of 2010, all appliances which need the third
prong will already include it. Not all outlets need to be
31 modified. Only those which will accommodate three-prong
plugs such as those for washing machines. Old appliances
34 with round pins will continue to operate normally.
With this initiative, INMETRO expects to solve
existing problems with electrical outlets. At present, there are
37 around twelve different types on the market. It is not
uncommon to try to push the plug into an outlet without
being completely successful. If it is not totally pushed in, the
40 part that is left out becomes a great risk of accidents. With
the new standard plug such risk will be eliminated.
Appliances which will continue to operate with two-
43 prong plugs are televisions, DVDs, video games and
blenders. Those requiring the third prong are microwave
ovens, air conditioners, washing machines, and freezers.
Internet: <extra.globo.com/economia/materiais>; <www.tva.gov>; <www.istockphoto.com/file_closeu> (with adaptations).
the picture and text as reference, judge the following items.
"three-prong plugs" (L.4) are plugs with three prongs.
This text refers to items 36 through 50.
Coming changes in electrical outlets and plugs
1Do you ever pay attention to the plug when buying
appliances? From now on, you will have to. Based
on INMETRO’s regulations, a new law already in effect makes
4 grounding mandatory. Therefore, three-prong plugs will
become commonplace, giving extra work to consumers as
early as this year.
7 The third prong provides a path to ground along
which the electric current travels. Electrical outlets will also
have three-wire receptacles that accommodate electrical
10 cords with three-prong plugs. Most major appliances, such as
stoves, refrigerators, and computers, have three-prong plugs,
meaning that they are grounded. Most older homes do not
13 have three-wire receptacles. If yours does not, you should
have an electrician rewire the home to accommodate the
three-prong plugs. Although three-prong adapters (called
16 cheater plugs) can be purchased, they are not recommended
for permanent use. Also remember never to clip the third
prong off a plug to make it fit a two-hole outlet.
19 The idea behind grounding is to protect the people
who use metal encased appliances from electric shock.
The casing is connected directly to the ground prong. Thus,
22 INMETRO’s concern is solely with safety. People touching
a refrigerator, for instance, will not get any potentially fatal
shocks.
25 Changes will have been introduced gradually by
2009, so as not to cause a profound impact on the population.
Electrical outlets will already be available with the third
28 receptacle. However, this will be useless unless it is
grounded. By law, new constructions must have grounding.
As of 2010, all appliances which need the third
prong will already include it. Not all outlets need to be
31 modified. Only those which will accommodate three-prong
plugs such as those for washing machines. Old appliances
34 with round pins will continue to operate normally.
With this initiative, INMETRO expects to solve
existing problems with electrical outlets. At present, there are
37 around twelve different types on the market. It is not
uncommon to try to push the plug into an outlet without
being completely successful. If it is not totally pushed in, the
40 part that is left out becomes a great risk of accidents. With
the new standard plug such risk will be eliminated.
Appliances which will continue to operate with two-
43 prong plugs are televisions, DVDs, video games and
blenders. Those requiring the third prong are microwave
ovens, air conditioners, washing machines, and freezers.
Internet: <extra.globo.com/economia/materiais>; <www.tva.gov>; <www.istockphoto.com/file_closeu> (with adaptations).
According to the text,
INMETRO has made a selection of the best plugs on the market.
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