(UNIT)

As vezes é fácil perceber que uma reação química está acontecendo devido à produção de luz ou calor, à mudança de cor, à expansão de gases, fenômenos físicos que ocorrem simultaneamente e não devem ser confundidos com as transformações químicas. De forma simbólica, essas transformações podem ser representadas por meio de equações químicas. O fenômeno de produção gasosa é observado quando uma solução de ácido sulfúrico, H₂SO₄ (aq), reage, inicialmente com quantidade suficiente de carbonato de cálcio, CaCO₃ (s), como no béquer da figura.

Considerando-se as informações do texto e a reação química que ocorre, em meio aquoso, no béquer, é correto afirmar:

(IFSP) Ana estava participando de uma gincana na escola em que estuda e uma das questões que ela tinha de responder era “quanto vale a soma das medidas dos ângulos internos do polígono regular da figura?”

Para responder a essa pergunta, ela lembrou que seu professor ensinou que a soma das medidas dos ângulos internos de um triângulo é igual a 180º, e que todo polígono pode ser decomposto em um número mínimo de triângulos. Sendo assim, Ana respondeu corretamente à pergunta dizendo:

Alguns especialistas argumentam que deveria haver rótulos climáticos na comida, da mesma forma que há informações sobre nutrição. Em teoria, os rótulos poderiam ajudar os consumidores a escolher produtos de baixo impacto ambiental e dariam aos agricultores e produtores mais incentivos para mudarem seus produtos.

The New York Times. Como fazer compras, cozinhar e comer em um mundo que está aquecendo? Disponível em: www.folha.uol.com.br. Acesso em: 6 maio 2019 (adaptado).

Considerando a proposta apresentada pelo texto, um dado que poderia constar nos rótulos de alimentos seria o de

(PUC-RJ) TEXTO: Driverless automobiles - The car that parks itself

CARS that need no driver are just around the corner according to researchers who have been testing vehicles bristling with aerials and cameras on public roads in America. However, researchers do not make cars, so it will be up to firms that do to bring the technology to market. And carmakers are a conservative bunch. Still, slowly and steadily the autonomous car will arrive, with the help of an increasing number of automated driving aids. A Swedish carmaker has recently demonstrated one such feature: a car that really does park itself.

Some cars already have systems that assist with parking, but these are not completely autonomous. They can identify an empty parallel-parking space and steer into it while the driver uses the brake. The Swedish system, however, lets the driver get out and use a smartphone application to instruct the vehicle to park. The car then ¹trundles off, manoeuvres into a parking place and sends a message to the driver to inform him where it is. The driver can collect the car in person or use his phone to call it back to where he dropped it off. Autonomous parking could thus be provided at places like shopping centers and airports, which are controlled areas in which automated vehicles can be managed more easily than on open highways.  In the past, designs for doing this have relied on car parks being fitted with buried guide wires that a vehicle can follow to an empty bay. That, though, creates ²a chicken-and-egg problem: car-park operators will not invest in such infrastructure until there is a sufficient number of suitably equipped cars on the road. Drivers, conversely, will not want to buy self-parking cars if there is nowhere to use them.

This means, as a safety engineer working on the project observes, that for autonomous parking to work most of the technology will have to be in the car itself. The test car, which looks like a normal car, therefore uses on-board GPS mapping, cameras with image-recognition software, and radar sensors to find its own way around a car park and avoid pedestrians and non-autonomous vehicles. The same engineer says the system is five to ten years from commercial deployment. If it proves a success then infrastructure might adapt to it, for instance by packing cars into tighter spaces. If there is no one in them there is no need to make room for their doors to open.

Driverless cars would also need to communicate with one another, to enhance safety. That, too, is coming. ³A number of carmakers are developing wireless networking systems through which vehicles can exchange data, such as their speed, their steering angle and even their weight, to forewarn anti-collision systems and safety devices if an accident looks likely.

In the USA, for example, a carmaker recently tested a brake light that can provide an early warning to other motorists. If the brakes are applied hard in an emergency, a signal is broadcast. This illuminates a warning light in the dashboard of suitably equipped following vehicles, even if they are out of sight around a bend or not immediately behind the vehicle doing the braking.

The American company has been testing this system as part of a collaborative research project with several European carmakers. ⁴They have put a fleet of 150 experimental vehicles on the roads. When they tested a group of these, the Americans found the technology let drivers brake much earlier, helping avoid collisions. A driverless car would be able to react even faster.

Another member of the research group has been testing driverless cars on roads around Munich— including belting down some of Germany’s high-speed autobahns. ⁵The ordinary-looking models use a variety of self-contained guidance systems. These include cameras mounted on the upper windscreen, which can identify road markings, signs and various obstacles likely to be encountered on roads.

The German cars also use a radar, to gauge how far the vehicle is from other cars and potential obstacles, and a lidar, which works like a radar but at optical frequencies. The lidar employs laser beams to scan the road ahead and builds up from the reflections a three-dimensional image of what this looks like. The image is processed by a computer in the vehicle, which also collects and compares data from a high-accuracy GPS unit. A series of ultrasonic sonars similar to those used in vehicles to provide parking assistance are placed around the car to add to the virtual picture. And just to make sure, a set of accelerometers provide an inertial navigation system that double-checks the vehicle’s position on the road.

⁶Although these cars can be switched to an autonomous driving mode, they are still required to have someone in the driving seat who can take over in the event of any difficulty. Some cars can steer themselves, slow down, brake and accelerate, even changing lanes to overtake slower vehicles.

From the print edition: Science and Technology Jun 29^th 2013

The word “Although” (ref. 6) introduces 

(UTFPR) Durante a Idade Média, as feiras caracterizavam-se por: