Questões de Concurso

Text 18A3-I 

    The roar of a waterfall suggests the power of water. Rampaging floodwaters can uproot strong trees and twist railroad tracks. When the power of water is harnessed, however, it can do useful work for humans. 

    Since ancient times, people have put the energy in the flow of water to work. They first made water work for them with the waterwheel, a wheel with paddles around its rim. Flowing water rotated the waterwheel, which in turn ran machinery that was linked to it. Today, new kinds of waterwheels — turbines — spin generators that produce electricity. Electricity from water-turned generators is known as hydroelectricity. 

    By building a dam across a river, the natural upstream water level is elevated and a difference in head is created that can be used to drive turbines and generate electricity. A large upstream reservoir may balance seasonal water flow; rain or melted snow can be stored in the reservoir during the wet season to provide electricity during dry seasons. 

    Waterpower is distributed unevenly among the continents and nations of the world. Europe and North America have developed much of their waterpower. Asia, South America, and Africa have abundant waterpower potential, but while countries such as China and Brazil have become leading hydroelectric producers, much of the waterpower resource on those continents remains undeveloped. 

Elizabeth Lachner. Hydroelectricity. Rosen Publishing Group, 2018 (adapted). 

Text 18A3-I 

    The roar of a waterfall suggests the power of water. Rampaging floodwaters can uproot strong trees and twist railroad tracks. When the power of water is harnessed, however, it can do useful work for humans. 

     Since ancient times, people have put the energy in the flow of water to work. They first made water work for them with the waterwheel, a wheel with paddles around its rim. Flowing water rotated the waterwheel, which in turn ran machinery that was linked to it. Today, new kinds of waterwheels – turbines – spin generators that produce electricity. Electricity from waterturned generators is known as hydroelectricity. 

     By building a dam across a river, the natural upstream water level is elevated and a difference in head is created that can be used to drive turbines and generate electricity. A large upstream reservoir may balance seasonal water flow; rain or melted snow can be stored in the reservoir during the wet season to provide electricity during dry seasons. 

    Waterpower is distributed unevenly among the continents and nations of the world. Europe and North America have developed much of their waterpower. Asia, South America, and Africa have abundant waterpower potential, but while countries such as China and Brazil have become leading hydroelectric producers, much of the waterpower resource on those continents remains undeveloped. 

Elizabeth Lachner. Hydroelectricity. Rosen Publishing Group, 2018 (adapted). 

 United Nations Environmental Programme. Dams and Development: Relevant Practices for Improved

Decision-making. Nairobi: The Secretariat of the Dams and Development Project, 2007. p. 10-1 (adapted).

Text 22A4-II 

      Over the past few years, Peruvian authorities have tried to find ways to manage increasing visitor numbers to the popular site which often had long lines and overcrowding, leaving many tourists unable to enter. Machu Picchu was awarded UNESCO World Heritage status in 1983 and is described by the awarding body as probably the most amazing urban creation of the Inca Empire at its height. It added its giant walls, terraces, and ramps “seem as if they have been cut naturally” into the continuous rock escarpments. The citadel, 130 km from Cusco, was built in the 15th as a religious sanctuary for the Incas at an altitude of 2,490 meters. 

      However, UNESCO also highlighted the challenges faced by the site, which it says requires more stringent management. “Tourism itself represents a double-edged sword by providing economic benefits but also by resulting in major cultural and ecological impacts,” said UNESCO. “The strongly increasing number of visitors to the historic sanctuary of Machu Picchu must be matched by an adequate management regulating access, diversifying the offer, and efforts to fully understand and minimize impacts. A larger appropriate and increasing share of the significant tourism revenues could be reinvested in planning and management.”. 

Internet: <https://www.thenationalnews.com> (adapted).