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A nanometer is a billionth of a meter. A DNA molecule is 2 nanometers in diameter. Protein molecules are about 10 nanometers in diameter. A human hair is 100,000 nanometers in diameter. But what is a nanometer and how does it relate to technology?
Nanotechnology is defined as the understanding and control of matter at dimensions of roughly 1 to 100 nanometers, a scale at which unique properties of materials emerge that can be used to develop novel technologies and products. At the nanoscale, the physical, chemical, and biological properties of materials differ from the properties of matter either at smaller scales, such as atoms, or at larger scales that we use in everyday life such as millimeters or inches.
Nanotechnology involves imaging, measuring, modeling, and manipulating matter only a few nanometers in size. Gold nanoparticles are made of the same material as in jewelry. But when light interacts with particles of gold, different colors are reflected. The different colors can be used in simple medical tests to indicate infection or disease. Metals such as copper become extremely rigid at the nanoscale, rather than bendable as in copper wires seen in everyday use.
What is the major difference between matter at the nanoscale and matter at larger scales such as millimeters or inches?
- A. At the nanoscale, metals are rigid, and at larger scales, they are bendable.
- B. Matter has different and special characteristics at the nanoscale.
- C. At the nanoscale, matter has different properties than matter at the atomic level.
- D. There is no difference.
Correct Answer: B
Rationale: The correct answer is B. Matter at the nanoscale exhibits unique and special characteristics that distinguish it from matter at larger scales. This can include properties like increased surface area, different melting points, altered conductivity, and enhanced reactivity. Choice A is incorrect as metals at the nanoscale can be more rigid compared to their larger scale counterparts. Choice C is incorrect because matter at the nanoscale has properties that are distinct from both atomic and larger scales. Choice D is incorrect as there are significant differences in how matter behaves and interacts at the nanoscale compared to larger scales.
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Today, bicycles are so common that it's hard to believe they haven't always been around. But two hundred years ago, bicycles didn't even exist, and the first bicycle, invented in Germany in 1818, was nothing like our bicycles today. It was made of wood and didn't even have pedals. Since then, however, numerous innovations and improvements in design have made the bicycle one of the most popular means of recreation and transportation around the world.
In 1839, Kirkpatrick Macmillan, a Scottish blacksmith, dramatically improved upon the original bicycle design. Macmillan's machine had tires with iron rims to keep them from getting worn down. He also used foot-operated cranks like pedals, so his bicycle could be ridden at a quick pace. It didn't look much like a modern bicycle, though, because its back wheel was substantially larger than its front wheel.
In 1861, the French Michaux brothers took bicycle design a step further by introducing a metal frame, making bicycles stronger and lighter. They also used rubber tires, which provided better traction and allowed for a more comfortable ride.
Finally, in 1874, the first truly modern bicycle appeared on the scene, complete with solid rubber tires, ball bearings, and even a chain drive, which enabled the rider to pedal at a higher speed with less effort. Today bicycles are built, used, and enjoyed all over the world.
Why did Macmillan add iron rims to the tires of his bicycle?
- A. Increase the weight of the bicycle.
- B. Enhance the durability of the tires.
- C. Reduce the bumpiness of the ride.
- D. Decrease the level of fatigue during the ride.
Correct Answer: B
Rationale: Macmillan added iron rims to his bicycle tires to enhance their durability and make them last longer. This innovation aimed to prevent the tires from getting worn down quickly. Adding weight to the bicycle (Choice A) was not the purpose of adding iron rims. While adding iron rims could potentially reduce the bumpiness of the ride (Choice C) by providing more stability, the main objective was to improve tire longevity. Similarly, reducing the level of fatigue during the ride (Choice D) was not the primary reason for adding iron rims.
Cystic fibrosis is a disease that is passed down through families. It is caused by a defective gene that makes the body produce abnormally thick and sticky fluid, called mucus. This mucus builds up in the breathing passages of the lungs and in the pancreas. The buildup of mucus results in life-threatening lung infections and serious digestion problems. The disease may also affect the sweat glands and a man's reproductive system. Millions of Americans carry a CF gene, but do not have symptoms. This is because a person with CF must inherit two defective genes, one from each parent. About 1 in 29 Caucasian Americans have the CF gene. It is more common among those of northern or central European descent. Most children with CF are diagnosed by age 2. For a small number, the disease is not detected until age 18 or older. These children often have a milder form of the disease.
Which of the following describes the purpose of the passage?
- A. To describe the causes of cystic fibrosis
- B. To explain how cystic fibrosis is passed down through families
- C. To provide an overview of CF and how it is inherited
- D. To review why some Americans have CF, but others do not
Correct Answer: C
Rationale: The correct answer is C. The passage aims to provide an overview of cystic fibrosis (CF) and how it is inherited. It explains that CF is passed down through families due to a defective gene, detailing how this gene affects the body and who is most commonly affected by the disease. Choices A, B, and D are incorrect because the passage does not solely focus on describing the causes of CF, explaining how it is passed down through families, or reviewing why some Americans have CF while others do not. Instead, it provides a broader perspective on CF and its inheritance.
The Moon has been worshipped by primitive peoples and has inspired humans to create everything from lunar calendars to love sonnets, but what do we really know about it? The most accepted theory about the origin of the Moon is that it was formed of the debris from a massive collision with the young Earth about 4.6 billion years ago. A huge body, perhaps the size of Mars, struck the Earth, throwing out an immense amount of debris that coalesced and cooled in orbit around the Earth.The development of Earth is inextricably linked to the Moon; the Moon's gravitational influence upon the Earth is the primary cause of ocean tides. In fact, the Moon has more than twice the effect upon the tides than does the Sun. The Moon makes one rotation and completes a revolution around the Earth every 27 days, 7 hours, and 43 minutes. This synchronous rotation is caused by an uneven distribution of mass in the Moon (essentially, it is heavier on one side than the other) and has allowed the Earth's gravity to keep one side of the Moon permanently facing Earth. It is an average distance from Earth of 384,403 km.The Moon has no atmosphere; without an atmosphere, the Moon has nothing to protect it from meteorite impacts, and thus the surface of the Moon is covered with impact craters, both large and small. The Moon also has no active tectonic or volcanic activity, so the erosive effects of atmospheric weathering, tectonic shifts, and volcanic upheavals that tend to erase and reform the Earth's surface features are not at work on the Moon. In fact, even tiny surface features such as the footprint left by an astronaut in the lunar soil are likely to last for millions of years, unless obliterated by a chance meteorite strike. The surface gravity of the Moon is about one-sixth that of the Earth's. Therefore, a man weighing 82 kilograms on Earth would only weigh 14 kilograms on the Moon.
What is the passage primarily about?
- A. What we know about the Moon and its differences from Earth
- B. A comparison of the Moon and Earth
- C. The Moon's effect on Earth
- D. The origin of the Moon
Correct Answer: A
Rationale: The correct answer is A: 'What we know about the Moon and its differences from Earth.' The passage discusses various aspects of the Moon, including its origin, gravitational influence on Earth, physical characteristics, lack of atmosphere, and surface features. It provides insights into what humans know about the Moon and highlights its differences from Earth. Choice B is incorrect because while the passage does compare certain aspects of the Moon and Earth, it primarily focuses on the Moon itself rather than a direct comparison. Choice C is incorrect as the passage briefly mentions the Moon's effect on Earth in relation to tides but does not primarily focus on this aspect. Choice D is incorrect as the origin of the Moon is mentioned in the passage, but it is not the primary focus of the text.
Today, bicycles are so common that it's hard to believe they haven't always been around. But two hundred years ago, bicycles didn't even exist, and the first bicycle, invented in Germany in 1818, was nothing like our bicycles today. It was made of wood and didn't even have pedals. Since then, however, numerous innovations and improvements in design have made the bicycle one of the most popular means of recreation and transportation around the world.
In 1839, Kirkpatrick Macmillan, a Scottish blacksmith, dramatically improved upon the original bicycle design. Macmillan's machine had tires with iron rims to keep them from getting worn down. He also used foot-operated cranks like pedals, so his bicycle could be ridden at a quick pace. It didn't look much like a modern bicycle, though, because its back wheel was substantially larger than its front wheel.
In 1861, the French Michaux brothers took bicycle design a step further by introducing a metal frame, making bicycles stronger and lighter. They also used rubber tires, which provided better traction and allowed for a more comfortable ride.
Finally, in 1874, the first truly modern bicycle appeared on the scene, complete with solid rubber tires, ball bearings, and even a chain drive, which enabled the rider to pedal at a higher speed with less effort. Today bicycles are built, used, and enjoyed all over the world.
What is the main idea of the passage?
- A. Bicycles have become a common mode of transportation worldwide.
- B. The first modern bicycle was invented in 1818 in Germany.
- C. Innovations and improvements in bicycle design have made bicycles popular for recreation and transportation globally.
- D. Bicycles are now built, used, and enjoyed globally.
Correct Answer: C
Rationale: The main idea of the passage is that innovations and improvements in bicycle design have made bicycles one of the most popular means of recreation and transportation worldwide. The passage outlines the evolution of bicycles from their early designs to the modern versions, emphasizing how these changes have contributed to their popularity. Choice A is incorrect because it focuses only on the current status of bicycles, while the main idea encompasses the evolution and improvements in design. Choice B is incorrect as it mentions the invention of the first modern bicycle but does not address the overall impact of innovations on bicycle popularity. Choice D is incorrect as it simply states a fact without capturing the essence of the passage, which is about the impact of design improvements.
Linking San Francisco to Marin County in California, the Golden Gate Bridge is one of the most famous bridges in the world. The bridge crosses over a narrow strait which connects the Pacific Ocean to San Francisco Bay. Prior to the bridge, people traveled by ferry boat across the strait. Although most people thought a bridge was necessary to expedite travel, some residents of the Bay area felt the risk of building the bridge was too great. Joseph Strauss believed that nothing was impossible, and dreams would never come to fruition if risks weren't taken. So, he decided to gather the best and brightest builders, architects, and workers to embark on the challenge of building a bridge across the Golden Gate Strait. With safety nets in place, the construction began in 1937. Building the anchorages first, the builders then moved on to the towers on each end, and then to the three-foot-thick cables to support the suspension bridge. Lastly, workers labored to complete the roadway which became the most dangerous and treacherous part of the entire task. The builders had to keep the bridge balanced, so it wouldn't fall into the bay. Today, over sixty-five years later, the bridge remains a lifeline for the people of the San Francisco Bay Area
Why did Strauss set up a net during the construction of the Golden Gate Bridge?
- A. For suspension
- B. For balance
- C. For aesthetics
- D. For safety
Correct Answer: D
Rationale: Strauss set up a net to ensure the safety of the workers in case of falls during the construction of the Golden Gate Bridge. Safety nets were essential to protect the workers from potential accidents or falls while working on the bridge. Choice A ('For suspension') is incorrect as safety nets were not used for suspension purposes but rather for worker safety. Choice B ('For balance') is incorrect as the balance of the bridge was maintained by other construction elements, not safety nets. Choice C ('For aesthetics') is incorrect as safety nets are not related to the visual appearance of the bridge but rather to the protection of the workers.