Questões - AFA | Gabarito e resoluções

(AFA - 2018) Quando necessrio, use: Acelerao da gravidade: g = 10 m/s2; sen 19 = cos 71 = 0,3; sen 71 = cos 19 = 0,9; Velocidade da luz no vcuo: c = 3,0 108m/s; Constante de Planck: h = 6,6 10-34J s; 1 eV = 1,6 1019J; Potencial eltrico no infinito: zero. Dois recipientes A e B, contendo o mesmo volume de gua, so colocados separadamente sobre duas balanas I e II, respectivamente, conforme indicado na figura a seguir. A nica diferena entre os recipientes A e B est no fato de que B possui um ladro que permite que a gua escoe para um outro recipiente C, localizado fora das balanas. Em seguida, mergulha-se, lentamente, sem girar e com velocidade constante, por meio de um fio ideal, em cada recipiente, um cilindro metlico, macio, de material no homogneo, de tal forma que o seu eixo sempre se mantm na vertical. Os cilindros vo imergindo na gua, sem provocar variao de temperatura e sem encostar nas paredes e nos fundos dos recipientes, de tal forma que os lquidos, nos recipientes A e B, sempre estaro em equilbrio hidrosttico no momento da leitura nas balanas. O grfico que melhor representa a leitura L das balanas I e II, respectivamente, LI e LII, em funo da altura h submersa de cada cilindro

(AFA - 2018) Quando necessrio use: - Acelereao da gravidade: g = 10 m/s2; - sen 19 = cos 71 = 0,3; - sen 71 = cos 19 = 0,9; - Velocidade da luz no vcuo: c = 3,0108m/s; - Constante de Planck: h = 6,610-34Js; - 1 eV = 1,610-19J; Uma rampa, homognea, de massa m e comprimento L, inicialmente colocada na horizontal. A extremidade A,dessa rampa, encontra-se acoplada a uma articulao sem atrito. Na extremidade Best sentado, em repouso, um garoto, tambm de massa m.Essa extremidade Best presa ao cho, por um fio ideal, e ao teto, por uma mola ideal, de constante elstica k, conforme ilustra a Figura 1. Em um determinado instante o garoto corta o fio. A mola, que est inicialmente deformada de um valorx,passa a erguer lentamente a extremidade B da rampa,fazendo com que o garoto escorregue, sem atrito e sem perder o contato com a rampa, at a extremidade A,conforme Figura 2. Quando o garoto, que neste caso deve ser tratado como partcula, atinge a extremidadeA,a mola se encontra em seu comprimento natural (sem deformao) e a rampa estar em repouso e inclinada de um ngulo. Considerando go mdulo da acelerao da gravidade local, nessas condies, a velocidade do garoto em A, vale

(AFA - 2018) Quando necessrio use : - Acelerao da gravidade: - sen 19C = cos 71 = 0,3; - sen 71 = cos 19 = 0,9; - Velocidade da luz no vcuo: - Constante de Planck: - 1 e V =; - Potencial eltrico no infinito: zero. Considere dois tubos cilndricos (1 e 2), verticais, idnticos e feitos do mesmo material, contendo um mesmo lquido em equilbrio at a altura de 50,0 cm ,conforme figura a seguir. As temperaturas nos dois tubos so inicialmente iguais e de valor 35CO tubo 1 resfriado at 0Cenquanto o tubo 2 aquecido at 70Ce a altura do lquido em cada tubo passa a ser o valor indicado na figura. Sabendo-se que o coeficiente de dilatao trmica dos tubos desprezvel quando comparado com o do lquido, o coeficiente de dilatao volumtrica do lquido, considerado constante, , em

(AFA - 2018) Quando necessrio, use: Acelerao da gravidade: Velocidade da luz no vcuo: Constante de Planck: Potencial eltrico no infinito: zero. Uma partcula abandonada sobre um plano inclinado, a partir do repouso no ponto A, de altura h,como indicado pela figura (fora de escala). Aps descer o plano inclinado, a partcula se move horizontalmente at atingir o ponto B.As foras de resistncia ao movimento de A at B so desprezveis. A partir do ponto B,a partcula ento cai, livre da ao de resistncia do ar, em um poo de profundidade igual a 3h e dimetro x.Ela colide com o cho do fundo do poo e sobe, em uma nova trajetria parablica at atingir o ponto C,o mais alto dessa nova trajetria. Na coliso com o fundo do poo a partcula perde 50%de sua energia mecnica. Finalmente, do ponto C ao ponto D, apartcula move-se horizontalmente experimentando atrito com a superfcie. Aps percorrer a distncia entre C e D, igual a 3h, a partcula atinge o repouso. Considerando que os pontosB e Cesto na borda do poo, que o coeficiente de atrito dinmico entre a partcula e o trecho igual a 0,5e que durante a coliso com o fundo do poo a partcula no desliza, a razo entre o dimetro do poo e a altura de onde foi abandonada a partcula,vale

(AFA - 2018) Um sistema gasoso constitudo por n mols de um gs perfeito passa do estado x para o estado y por meio dos processos distintos 1 e 2 mostrados no esquema a seguir. Se no processo 2 o sistema realiza um trabalho de 200 Je absorve uma quantidade de calor de 500 J correto afirmar que

(AFA - 2018) PROVA DE REDAO Com base nos textos abaixo e nos textos da prova de Lngua Portuguesa, bem como no seu conhecimento de mundo, escreva um texto dissertativo-argumentativo, em prosa, sobre a seguinte questo: Os efeitos negativos do uso indiscriminado da internet TEXTO I A partilha de informaes ganhou propores nunca imaginadas com a popularizao das redes sociais. Ganhamos agilidade na troca de informaes e estamos mais prximos. Mas a troca indiscriminada de informaes descontextualizadas e humor porttil deixa uma questo em aberto: estamos perdendo o senso crtico? (http://obviousmag.org/archives/2011/09/redes_sociais_e_colaboracao_extrema_O_fim_do_senso_critico-.html.Fragmento.Acesso em: 21 fev 2017) TEXTO II (SALIMENA, Raphael.In:jottaclub.com/2017/02/comisao-de-educasao-do-senado-imajina-qe-seja-a-ora-de-mudar-portugues-emnova-reforma-ortografica/.Acesso em: 11 mar 2017) Observao: D um ttulo redao. Orientaes a) Considere os textos desta prova como motivadores e fonte de dados. No os copie, sob pena de ter a redao zerada. b) A redao dever conter no mnimo 100 (cem) palavras, considerando-se palavras todas aquelas pertencentes s classes gramaticais da Lngua Portuguesa. c) Recomenda-se que a redao seja escrita em letra cursiva legvel. Caso seja utilizada letra de forma (caixa alta), as letras maisculas devero receber o devido realce. d) Utilize caneta de tinta preta ou azul.

(AFA - 2018) Um corpo M de dimenses desprezveis e massa 10 kg movimentando-se emuma dimenso, inicialmente com velocidade V,vai sucessivamente colidindo inelasticamente com N partculas m, todas de mesma massa 1 kg, e com velocidades de mdulo v = 20 m/s, que tambm se movimentam em uma dimenso de acordo com a Figura 1, a seguir. O grfico que representa a velocidade final do conjunto vfaps cada coliso em funo do nmero de partculas N apresentado na Figura 2, a seguir. Desconsiderando as foras de atrito e a resistncia do ar sobre o corpo e as partculas, a coliso de ordem N0na qual a velocidade do corpo resultante (corpo M + N0 partculas m) se anula, ,

(AFA - 2018) TEXTO PARA A PRXIMA QUESTO. FOOD SHORTAGE CAUSES, EFFECTS AND SOLUTIONS Food shortage is a serious problem facing the world and is prevalent in sub-Saharan Africa. The scarcity of food is caused by economic, environmental and social factors such as crop failure, overpopulation and poor government policies are the main cause of food scarcity in most countries. Environmental factors determine the kind of crops to be produced in a given place, economic factors determine the buying and production capacity and socio-political factors determine distribution of food to the masses. Food shortage has far reaching long and short term negative impacts which include starvation, malnutrition, increased mortality and political unrest1. There is need to collectively address the issue of food insecurity using both emergency and long term measures. Causes of food shortages There are a number of social factors causing food shortages. The rate of population increase is higher than increase in food production. The world is consuming more than it is producing, leading to decline in food stock and storage level and increased food prices due to soaring2 demand. Increased population has led to clearing of agricultural land for human settlement reducing agricultural production (Kamdor, 2007). Overcrowding of population in a given place results in urbanization of previously rich agricultural fields. Destruction of forests for human settlement, particularly tropical rain forest has led to climatic changes, such as prolonged droughts and desertification. Population increase means more pollution as people use more fuel in cars, industry, domestic cooking. The resultant effect is increased air and water pollution which affect the climate and food production. Environmental factors have greatly contributed to food shortage. Climatic change has reduced agricultural production. The change in climate is majorly caused by human activities and to some small extent natural activities. Increased combustion of fossil fuels due to increasing population through power plant, motor transport and mining of coal and oil emits green house gases which have continued to affect world climate. Deforestation of tropical forest due to human pressure has changed climatic patterns and rainfall seasons, and led to desertification which cannot support a crop production. Land degradation due to increased human activities has impacted negatively on agricultural production (Kamdor, 2007). Natural disasters such as floods, tropical storms and prolonged droughts are on the increase and have devastating impacts on food security particularly in developing countries. There are several economic factors that contribute to food shortage. Economic factors affect the ability of farmers to engage in agricultural production. Poverty situation in developing nations have reduced their capacity to produce food, as most farmers cannot afford seed and fertilizers. They use poor farming methods that cannot yield3 enough, even substantial use. Investments in agricultural research and developing are very low in developing nations. Recent global financial crisis have led to increase in food prices and reduced investments in agriculture by individuals and governments in developed nations resulting in reduced food production. Effects of food shortage There are a number of short term effects of food shortage. The impact on children, mothers and elderly are very evident as seen in malnutrition and hunger related deaths. Children succumb to hunger within short period as they cannot stand long period of starvation and they die even before the arrival of emergency assistance. There are also long term effects of food shortage. These include increase in the price of food as a result demand and supply forces. Increasing cost of food production due to the increase in fuel prices coupled with persistent drought in grain producing regions has contributed to the increase in the price of food in the world. Increase in oil price led to increase in the price of fertilizers, transportation of food and also industrial agriculture. Increasing food prices culminated in political instability and social unrest in several nations across the globe in 2007, in countries of Mexico, Cameroon, Brazil, Burkina Faso, Pakistan, Egypt and Bangladesh among other nations (Kamdor, 2007). Solution to problem of food shortage There are some solutions to the problem of food shortage. There is need to reduce production of carbon emissions and pollution to reduce the resultant climatic change through concerted and individual efforts. There is need to invest in clean energy such as solar, nuclear, and geothermal power in homes and industries, because they dont have adverse effects on the environment (Kamdor, 2007). Rich nations should help poor nations to develop and use clean and renewable energy in order to stabilize green house emissions into the atmosphere (Watson, nd). Government need to work in consultation with climatic bodies, World Bank and the UN to engage in projects aimed at promoting green environment. Conclusion Causes of food shortage are well known and can be solved if appropriate measures to solve the problem are taken and effectively implemented. Environmental causes of food shortages are changes in climatic and pollution due to human activities such overgrazing4 and deforestation which can be controlled through legislation. (Adapted from http://www.paypervids.com/food-shortage-causes- effects-solutions/Acesso em:14 fev 2017) Glossary: 1. unrest disagreement or fighting between different groups of people 2. soaring something that increases rapidly above the usual level 3. yield to supply or produce something such as profit or an amount or food 4. overgrazing excessive use of land where animals feed on grass In the sentence land degradation due to increased human activities has impacted negatively on agricultural production (destacado) it is INCORRECT to state that

(AFA - 2018) RAIOS CAUSAM 130 MORTES POR ANO NO BRASIL; SAIBA COMO PREVENIR Comeou a temporada de raios e o Brasil o lugar onde eles mais caem no mundo. Os raios so fenmenos da natureza impressionantes, mas causam mortes e prejuzos. Todos os anos morrem em mdia 130 pessoas no pas atingidas por essas descargas eltricas. (...) (...) Segundo as pesquisas feitas pelo grupo de eletricidade atmosfrica do INPE, o nmero de mortes por raios maior do que por deslizamentos e enchentes. E na primavera e no vero, poca com mais tempestades, que a preocupao aumenta (...) Disponvel em: ww1.g1.globo.com/bom-dia-brasil. Acesso em:16 fev.2017. Como se pode verificar na notcia acima, os raios causam mortes e, alm disso, constantemente h outros prejuzos ligados a eles: destruio de linhas de transmisso de energia e telefonia, incndios florestais, dentre outros. As nuvens se eletrizam devido s partculas de gelo que comeam a descer muito rapidamente, criando correntes de ar bastante bruscas, o que provoca frico entre gotas de gua e de gelo, responsvel pela formao e, consequentemente, a acumulao de eletricidade esttica. Quando se acumula carga eltrica negativa demasiadamente na zona inferior da nuvem (este o caso mais comum) ocorre uma descarga eltrica em direo ao solo (que por induo eletrosttica adquiriu cargas positivas). Considere que a base de uma nuvem de tempestade, eletricamente carregada com carga de mdulo igual a ,situa-se a acima do solo. O ar mantm-se isolante at que o campo eltrico entre a base da nuvem e o solo atinja o valor de Nesse instante a nuvem se descarrega por meio de um raio que dura Considerando que o campo eltrico na regio onde ocorreu o raio seja uniforme, a energia liberada neste raio , em joules, igual a

(AFA - 2018) Os carregadores de bateria sem fio de smartphones, tambm conhecidos como carregadores wireless, so dispositivos compostos de bobina e ligados rede eltrica, que carregam as baterias dos aparelhos apenas pela proximidade, atravs do fenmeno de induo eletromagntica. Para isso, o smartphone deve ser apto referida tecnologia, ou seja, tambm possuir uma bobina, para que nela surja uma fora eletromotriz induzida que carregar a bateria. Se na bobina de um carregador (indutora), paralela e concntrica com a bobina de um smartphone (induzida), passa uma corrente, comem segundos,o grfico que melhor representa a fora eletromotriz induzida () na bobina do smartphone, em funo do tempo

(AFA - 2018) TEXTO PARA A PRXIMA QUESTO. FOOD SHORTAGE CAUSES, EFFECTS AND SOLUTIONS Food shortage is a serious problem facing the world and is prevalent in sub-Saharan Africa. The scarcity of food is caused by economic, environmental and social factors such as crop failure, overpopulation and poor government policies are the main cause of food scarcity in most countries. Environmental factors determine the kind of crops to be produced in a given place, economic factors determine the buying and production capacity and socio-political factors determine distribution of food to the masses. Food shortage has far reaching long and short term negative impacts which include starvation, malnutrition, increased mortality and political unrest1. There is need to collectively address the issue of food insecurity using both emergency and long term measures. Causes of food shortages There are a number of social factors causing food shortages. The rate of population increase is higher than increase in food production. The world is consuming more than it is producing, leading to decline in food stock and storage level and increased food prices due to soaring2 demand. Increased population has led to clearing of agricultural land for human settlement reducing agricultural production (Kamdor, 2007). Overcrowding of population in a given place results in urbanization of previously rich agricultural fields. Destruction of forests for human settlement, particularly tropical rain forest has led to climatic changes, such as prolonged droughts and desertification. Population increase means more pollution as people use more fuel in cars, industry, domestic cooking. The resultant effect is increased air and water pollution which affect the climate and food production. Environmental factors have greatly contributed to food shortage. Climatic change has reduced agricultural production. The change in climate is majorly caused by human activities and to some small extent natural activities. Increased combustion of fossil fuels due to increasing population through power plant, motor transport and mining of coal and oil emits green house gases which have continued to affect world climate. Deforestation of tropical forest due to human pressure has changed climatic patterns and rainfall seasons, and led to desertification which cannot support a crop production. Land degradation due to increased human activities has impacted negatively on agricultural production (Kamdor, 2007). Natural disasters such as floods, tropical storms and prolonged droughts are on the increase and have devastating impacts on food security particularly in developing countries. There are several economic factors that contribute to food shortage. Economic factors affect the ability of farmers to engage in agricultural production. Poverty situation in developing nations have reduced their capacity to produce food, as most farmers cannot afford seed and fertilizers. They use poor farming methods that cannot yield3 enough, even substantial use. Investments in agricultural research and developing are very low in developing nations. Recent global financial crisis have led to increase in food prices and reduced investments in agriculture by individuals and governments in developed nations resulting in reduced food production. Effects of food shortage There are a number of short term effects of food shortage. The impact on children, mothers and elderly are very evident as seen in malnutrition and hunger related deaths. Children succumb to hunger within short period as they cannot stand long period of starvation and they die even before the arrival of emergency assistance. There are also long term effects of food shortage. These include increase in the price of food as a result demand and supply forces. Increasing cost of food production due to the increase in fuel prices coupled with persistent drought in grain producing regions has contributed to the increase in the price of food in the world. Increase in oil price led to increase in the price of fertilizers, transportation of food and also industrial agriculture. Increasing food prices culminated in political instability and social unrest in several nations across the globe in 2007, in countries of Mexico, Cameroon, Brazil, Burkina Faso, Pakistan, Egypt and Bangladesh among other nations (Kamdor, 2007). Solution to problem of food shortage There are some solutions to the problem of food shortage. There is need to reduce production of carbon emissions and pollution to reduce the resultant climatic change through concerted and individual efforts. There is need to invest in clean energy such as solar, nuclear, and geothermal power in homes and industries, because they dont have adverse effects on the environment (Kamdor, 2007). Rich nations should help poor nations to develop and use clean and renewable energy in order to stabilize green house emissions into the atmosphere (Watson, nd). Government need to work in consultation with climatic bodies, World Bank and the UN to engage in projects aimed at promoting green environment. Conclusion Causes of food shortage are well known and can be solved if appropriate measures to solve the problem are taken and effectively implemented. Environmental causes of food shortages are changes in climatic and pollution due to human activities such overgrazing4 and deforestation which can be controlled through legislation. (Adapted from http://www.paypervids.com/food-shortage-causes- effects-solutions/Acesso em:14 fev 2017) Glossary: 1. unrest disagreement or fighting between different groups of people 2. soaring something that increases rapidly above the usual level 3. yield to supply or produce something such as profit or an amount or food 4. overgrazing excessive use of land where animals feed on grass Investing in clean energy is considered

(AFA - 2018) TEXTO PARA A PRXIMA QUESTO. FOOD SHORTAGE CAUSES, EFFECTS AND SOLUTIONS Food shortage is a serious problem facing the world and is prevalent in sub-Saharan Africa. The scarcity of food is caused by economic, environmental and social factors such as crop failure, overpopulation and poor government policies are the main cause of food scarcity in most countries. Environmental factors determine the kind of crops to be produced in a given place, economic factors determine the buying and production capacity and socio-political factors determine distribution of food to the masses. Food shortage has far reaching long and short term negative impacts which include starvation, malnutrition, increased mortality and political unrest1. There is need to collectively address the issue of food insecurity using both emergency and long term measures. Causes of food shortages There are a number of social factors causing food shortages. The rate of population increase is higher than increase in food production. The world is consuming more than it is producing, leading to decline in food stock and storage level and increased food prices due to soaring2 demand. Increased population has led to clearing of agricultural land for human settlement reducing agricultural production (Kamdor, 2007). Overcrowding of population in a given place results in urbanization of previously rich agricultural fields. Destruction of forests for human settlement, particularly tropical rain forest has led to climatic changes, such as prolonged droughts and desertification. Population increase means more pollution as people use more fuel in cars, industry, domestic cooking. The resultant effect is increased air and water pollution which affect the climate and food production. Environmental factors have greatly contributed to food shortage. Climatic change has reduced agricultural production. The change in climate is majorly caused by human activities and to some small extent natural activities. Increased combustion of fossil fuels due to increasing population through power plant, motor transport and mining of coal and oil emits green house gases which have continued to affect world climate. Deforestation of tropical forest due to human pressure has changed climatic patterns and rainfall seasons, and led to desertification which cannot support a crop production. Land degradation due to increased human activities has impacted negatively on agricultural production (Kamdor, 2007). Natural disasters such as floods, tropical storms and prolonged droughts are on the increase and have devastating impacts on food security particularly in developing countries. There are several economic factors that contribute to food shortage. Economic factors affect the ability of farmers to engage in agricultural production. Poverty situation in developing nations have reduced their capacity to produce food, as most farmers cannot afford seed and fertilizers. They use poor farming methods that cannot yield3 enough, even substantial use. Investments in agricultural research and developing are very low in developing nations. Recent global financial crisis have led to increase in food prices and reduced investments in agriculture by individuals and governments in developed nations resulting in reduced food production. Effects of food shortage There are a number of short term effects of food shortage. The impact on children, mothers and elderly are very evident as seen in malnutrition and hunger related deaths. Children succumb to hunger within short period as they cannot stand long period of starvation and they die even before the arrival of emergency assistance. There are also long term effects of food shortage. These include increase in the price of food as a result demand and supply forces. Increasing cost of food production due to the increase in fuel prices coupled with persistent drought in grain producing regions has contributed to the increase in the price of food in the world. Increase in oil price led to increase in the price of fertilizers, transportation of food and also industrial agriculture. Increasing food prices culminated in political instability and social unrest in several nations across the globe in 2007, in countries of Mexico, Cameroon, Brazil, Burkina Faso, Pakistan, Egypt and Bangladesh among other nations (Kamdor, 2007). Solution to problem of food shortage There are some solutions to the problem of food shortage. There is need to reduce production of carbon emissions and pollution to reduce the resultant climatic change through concerted and individual efforts. There is need to invest in clean energy such as solar, nuclear, and geothermal power in homes and industries, because they dont have adverse effects on the environment (Kamdor, 2007). Rich nations should help poor nations to develop and use clean and renewable energy in order to stabilize green house emissions into the atmosphere (Watson, nd). Government need to work in consultation with climatic bodies, World Bank and the UN to engage in projects aimed at promoting green environment. Conclusion Causes of food shortage are well known and can be solved if appropriate measures to solve the problem are taken and effectively implemented. Environmental causes of food shortages are changes in climatic and pollution due to human activities such overgrazing4 and deforestation which can be controlled through legislation. (Adapted from http://www.paypervids.com/food-shortage-causes- effects-solutions/Acesso em:14 fev 2017) Glossary: 1. unrest disagreement or fighting between different groups of people 2. soaring something that increases rapidly above the usual level 3. yield to supply or produce something such as profit or an amount or food 4. overgrazing excessive use of land where animals feed on grass The sentence the change in climate is majorly caused by human activities (lines 36 and 37) means that

(AFA - 2018) Quando necessrio use: - Acelereao da gravidade: g = 10 m/s2; - sen 19 = cos 71 = 0,3; - sen 71 = cos 19 = 0,9; - Velocidade da luz no vcuo: c = 3,0108m/s; - Constante de Planck: h = 6,610-34Js; - 1 eV = 1,610-19J; - Potencial eltrico no infinito: zero. SECA VIRA TEMA DE EXCURSO E AULA DE CINCIA EM ESCOLAS Thais Bilenky de So Paulo 26/10/2014 02h00 (...) Como no Vera Cruz, a crise da gua tem motivado atividades em diversos colgios da cidade. Na rede municipal, 34escolas ficaram sem gua na semana passada. A Secretaria de Educao diz que incentiva debates sobre o tema e sua incluso em projetos interdisciplinares. Nas escolas particulares, problemas de abastecimento no so comuns. A falta de gua abordada para efeito pedaggico como no colgio Rio Branco, que tem promovido bate-papos e estudos. (...) Disponvel em: www1.folha.uol.com.br/cotidiano. Acesso em: 14 fev. 2017. Motivado pelo trecho do artigo acima exposto, um professor de fsica lanou um desafio para os alunos do 3 ano em uma escola onde, frequentemente, falta gua. Tal desafio consistia em determinar o volume dgua em um reservatrio de difcil acesso. Para a determinao deste volume dgua os alunos deveriam utilizar somente um circuito eltrico constitudo de um voltmetro ideal V,uma bateria de femigual a 12 Ve resistncia interna igual a 1, alm de um resistor hmico Rigual a 2e um reostato AB,feito de material de resistividade eltrica constante, cuja resistncia eltrica pode variar de 0a 4,de acordo com a posio da boia que ajustada pela altura do nvel dgua do reservatrio. Depois de algum tempo, os alunos apresentaram o projeto ao professor, conforme esquematizado na figura a seguir. De acordo com o projeto, o volume dgua no reservatrio pode ser calculado por meio da ddp nos terminais da bateria, registrada pelo voltmetro. Sendo a capacidade mxima deste reservatrio igual a 20 m3,desconsiderando as resistncias eltricas dos fios de ligao que esto isolados e o atrito do suporte da boia com o reostato, quando o voltmetro indicar 9,0 V,o volume dgua neste reservatrio ser, em m3, igual a:

(AFA - 2018) TEXTO PARA A PRXIMA QUESTO. FOOD SHORTAGE CAUSES, EFFECTS AND SOLUTIONS Food shortage is a serious problem facing the world and is prevalent in sub-Saharan Africa. The scarcity of food is caused by economic, environmental and social factors such as crop failure, overpopulation and poor government policies are the main cause of food scarcity in most countries. Environmental factors determine the kind of crops to be produced in a given place, economic factors determine the buying and production capacity and socio-political factors determine distribution of food to the masses. Food shortage has far reaching long and short term negative impacts which include starvation, malnutrition, increased mortality and political unrest1. There is need to collectively address the issue of food insecurity using both emergency and long term measures. Causes of food shortages There are a number of social factors causing food shortages. The rate of population increase is higher than increase in food production. The world is consuming more than it is producing, leading to decline in food stock and storage level and increased food prices due to soaring2 demand. Increased population has led to clearing of agricultural land for human settlement reducing agricultural production (Kamdor, 2007). Overcrowding of population in a given place results in urbanization of previously rich agricultural fields. Destruction of forests for human settlement, particularly tropical rain forest has led to climatic changes, such as prolonged droughts and desertification. Population increase means more pollution as people use more fuel in cars, industry, domestic cooking. The resultant effect is increased air and water pollution which affect the climate and food production. Environmental factors have greatly contributed to food shortage. Climatic change has reduced agricultural production. The change in climate is majorly caused by human activities and to some small extent natural activities. Increased combustion of fossil fuels due to increasing population through power plant, motor transport and mining of coal and oil emits green house gases which have continued to affect world climate. Deforestation of tropical forest due to human pressure has changed climatic patterns and rainfall seasons, and led to desertification which cannot support a crop production. Land degradation due to increased human activities has impacted negatively on agricultural production (Kamdor, 2007). Natural disasters such as floods, tropical storms and prolonged droughts are on the increase and have devastating impacts on food security particularly in developing countries. There are several economic factors that contribute to food shortage. Economic factors affect the ability of farmers to engage in agricultural production. Poverty situation in developing nations have reduced their capacity to produce food, as most farmers cannot afford seed and fertilizers. They use poor farming methods that cannot yield3 enough, even substantial use. Investments in agricultural research and developing are very low in developing nations. Recent global financial crisis have led to increase in food prices and reduced investments in agriculture by individuals and governments in developed nations resulting in reduced food production. Effects of food shortage There are a number of short term effects of food shortage. The impact on children, mothers and elderly are very evident as seen in malnutrition and hunger related deaths. Children succumb to hunger within short period as they cannot stand long period of starvation and they die even before the arrival of emergency assistance. There are also long term effects of food shortage. These include increase in the price of food as a result demand and supply forces. Increasing cost of food production due to the increase in fuel prices coupled with persistent drought in grain producing regions has contributed to the increase in the price of food in the world. Increase in oil price led to increase in the price of fertilizers, transportation of food and also industrial agriculture. Increasing food prices culminated in political instability and social unrest in several nations across the globe in 2007, in countries of Mexico, Cameroon, Brazil, Burkina Faso, Pakistan, Egypt and Bangladesh among other nations (Kamdor, 2007). Solution to problem of food shortage There are some solutions to the problem of food shortage. There is need to reduce production of carbon emissions and pollution to reduce the resultant climatic change through concerted and individual efforts. There is need to invest in clean energy such as solar, nuclear, and geothermal power in homes and industries, because they dont have adverse effects on the environment (Kamdor, 2007). Rich nations should help poor nations to develop and use clean and renewable energy in order to stabilize green house emissions into the atmosphere (Watson, nd). Government need to work in consultation with climatic bodies, World Bank and the UN to engage in projects aimed at promoting green environment. Conclusion Causes of food shortage are well known and can be solved if appropriate measures to solve the problem are taken and effectively implemented. Environmental causes of food shortages are changes in climatic and pollution due to human activities such overgrazing4 and deforestation which can be controlled through legislation. (Adapted from http://www.paypervids.com/food-shortage-causes- effects-solutions/Acesso em:14 fev 2017) Glossary: 1. unrest disagreement or fighting between different groups of people 2. soaring something that increases rapidly above the usual level 3. yield to supply or produce something such as profit or an amount or food 4. overgrazing excessive use of land where animals feed on grass The text conclusion seems to be

(AFA - 2018) Em muitos problemas de fsica desprezam-se as foras de resistncia ao movimento. Entretanto, sabe-se que, na prtica, essas foras so significativas e muitas vezes desempenham um papel determinante. Por exemplo, no automobilismo, os veculos comumente possuem dispositivos aerodinmicos implementados, os quais tm a funo de contribuir para o aumento da Downforce, uma fora vertical, inversa sustentao, que busca incrementar a aderncia dos pneus ao asfalto atravs de um acrscimo na carga normal, permitindo que o veculo possa realizar as curvas com uma velocidade maior do que o faria sem estes dispositivos. (Trecho retirado da monografia intitulada Sistema ativo de reduo de arrasto aerodinmico por atuador aplicado a um prottipo de frmula SAE, de autoria de Danilo Barbosa Porto, apresentada na Escola de Engenharia de So Carlos, da Universidade de So Paulo, em 2016). Para avaliar o papel da Downforce, considere um carro de Frmula 1, de massa M, realizando uma curva em determinada pista plana. Ao se desprezar completamente os efeitos produzidos pelo seu movimento em relao ao ar, mas considerando o atrito entre pneus e o asfalto, o carro consegue fazer a curva, sem derrapar, a uma velocidade mxima V. Porm, ao levar em conta, especificamente, a atuao da Downforce D (desconsiderando a fora de arrasto) a velocidade mxima V do carro, nessa mesma curva, muda em funo de D. Nessas condies, o grfico que melhor representa a relao em funo de D