Обучение чтению и устной речи на английском языке по специальности «Физика»
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Тематика:
Английский язык
Автор:
Дедушенко Ирина Семеновна
Год издания: 2012
Кол-во страниц: 52
Дополнительно
Вид издания:
Учебно-методическая литература
Уровень образования:
ВО - Бакалавриат
Артикул: 840501.01.99
В каждом из трех уроков содержатся словарь, три текста и задания, позволяющие контролировать понимание текстов. Грамматические упражнения направлены на повторение наиболее сложных конструкций английского языка.
Для студентов старших курсов, обучающихся по специальности «Физика» (кафедра ФН-4).
Тематика:
ББК:
УДК:
ОКСО:
- ВО - Бакалавриат
- 00.03.38: Физика
- 03.03.01: Прикладные математика и физика
- ВО - Специалитет
- 03.05.02: Фундаментальная и прикладная физика
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Московский государственный технический университет имени Н.Э. Баумана И.С. Дедушенко Обучение чтению и устной речи на английском языке по специальности «Физика» Методические указания Москва Издательство МГТУ им. Н.Э. Баумана 2012
УДК 802.0 ББК 81.2 Англ-923 Д26 Рецензент И.В. Стасенко Дедушенко И.С. Обучение чтению и устной речи на английском языке по специальности «Физика» : метод. указания / И.С. Дедушенко. — М.: Изд-во МГТУ им. Н.Э. Баумана, 2012. — 49, [3] с. В каждом из трех уроков содержатся словарь, три текста и задания, позволяющие контролировать понимание текстов. Грамматические упражнения направлены на повторение наиболее сложных конструкций английского языка. Для студентов старших курсов, обучающихся по специальности «Физика» (кафедра ФН-4). УДК 802.0 ББК 81.2 Англ-923 МГТУ им. Н.Э. Баумана, 2012 Д26
ПРЕДИСЛОВИЕ Данные методические указания предназначены для обучения студентов-физиков старших курсов чтению, переводу научно-технической литературы на английском языке, навыкам реферирования и аннотирования, а также умению дискутировать на профессиональные темы. Перед чтением основного текста урока рекомендуется ознакомиться с предваряющим текст вокабуляром. Усвоение терминов облегчает дальнейшее беспереводное понимание текстов. Любая работа с текстом должна начинаться с просмотрового чтения, а не с дословного перевода. В разделе Discussion даны задания на понимание текста и применение материалов урока при обсуждении проблем по физике. Этот раздел очень важен для обучения студентов навыкам устной речи, умению анализировать материал и логически строить ответ. Эти навыки и умения позволят студенту подготовиться к презентации доклада на конференции, а также с легкостью вести беседу на профессиональную тему и обсуждать научные проблемы. Грамматические упражнения составлены таким образом, что обеспечивают повторение наиболее сложных конструкций английского языка, таких, как образование множественного числа существительных латинского и греческого происхождения, неличные формы глагола. Предложенный грамматический материал необходим для правильного перевода статей по физике, а также для ведения научной беседы. Методические указания помогут будущим специалистам в области физики лучше ориентироваться в огромном потоке публикаций на английском языке, определять их ценность и постоянно повышать свой профессиональный уровень.
Unit 1. THREE NEWTON’S LAWS Memorize the following vocabulary to text 1A. center-of-mass acceleration — центр инерционной массы conversion n — превращение, преобразование, переход converse v — преобразовывать exert v — прилагать усилия, напрягать силы downward force — сила, направленная вниз total force — результирующая (полная, суммарная) сила upward force — подъемная сила; сила, направленная вверх let down v — опускать, спускать; ослаблять, замедлять, снижать negligible adj — ничтожный, не принимаемый в расчет on the order of — порядка … pull up v — натягивать side-effect — побочный эффект speed up v — ускорять stick, stuck v — задерживать, останавливать streamlined adj — обтекаемый, четкий taper off v — сужаться, убывать по конусу terminal velocity — конечная скорость vanquish v — преодолевать, побеждать velocity n — 1. скорость; 2. вектор скорости weigh v — взвешивать weight n — вес
Text 1A. Newton’s First Law Read and translate the text. Study the examples given in the text. If the total force on an object is zero, its center of mass continues in the same state of motion. In other words, an object initially at rest is predicted to remain at rest if the total force on it is zero, and an object in motion remains in motion with the same velocity in the same direction. The converse of Newton’s first law is also true: if we observe an object moving with constant velocity along a straight line, then the total force on it must be zero. What happens if the total force on an object is not zero? It accelerates. For example: An elevator has a weight of 5000 N. Compare the forces that the cable must exert to raise it at constant velocity, lower it at constant velocity, and just keep it hanging. Answer: In all three cases the cable must pull up with a force of exactly 5000 N. Most people think you’d need at least a little more than 5000 N to make it go up, and a little less than 5000 N to let it down, but that’s incorrect. Extra force from the cable is only necessary for speeding the car up when it starts going up or slowing it down when it finishes going down. Decreased force is needed to speed the car up when it gets going down and to slow it down when it finishes going up. But when the elevator is cruising at constant velocity, Newton’s first law says that you just need to cancel the force of the earth’s gravity. It seems that the statement in the example that the cable’s upward force “cancels” the earth’s downward gravitational force implies that there has been a contest, and the cable’s force has won, vanquishing the earth’s gravitational force and making it disappear. We know that both forces continue to exist because they both have side-effects other than their effects on the car’s centre-of-mass motion. That is incorrect. Both forces continue to exist, but because they add up numerically to zero, the elevator has no center-of-mass acceleration. The force acting
between the cable and the car continues to produce tension in the cable and keep the cable taut. The earth's gravitational force continues to keep the passengers (whom we are considering as part of the elevator-object) stuck to the floor and to produce internal stresses in the walls of the car, which must hold up the floor. Example 2 (terminal velocity for falling objects): An object like a feather that is not dense or streamlined does not fall with constant acceleration, because air resistance is nonnegligible. In fact, its acceleration tapers off to nearly zero within a fraction of a second, and the feather finishes dropping at constant speed (known as its terminal velocity). Why does this happen? Newton’s first law tells us that the total force on the feather must have been reduced to nearly zero after a short time. There are two forces acting on the feather: a downward gravitational force from the planet earth, and an upward frictional force from the air. As the feather speeds up, the air friction becomes stronger and stronger, and eventually it cancels out the earth’s gravitational force, so the feather just continues with constant velocity without speeding up any more. The situation for a skydiver is exactly analogous. It’s just that the skydiver experiences perhaps a million times more gravitational force than the feather, and it is not until she is falling very fast that the force of air friction becomes as strong as the gravitational force. It takes her several seconds to reach terminal velocity, which is on the order of a hundred miles per hour. (2885) Tasks to text 1A 1. Give the definition of the First Newton’s Law. 2. What forces act on a falling object? 3. What fields of physics can the First Newton’s Law be applied to? 4. Give your own examples of the First Newton’s Law application.
Text 1B. Newton’s Second Law Read the text and state what acceleration is. What about cases where the total force on an object is not zero, so that Newton’s first law doesn’t apply? The object will have acceleration. The way positive and negative signs of force and acceleration are defined guarantees that positive forces produce positive accelerations, and likewise for negative values. How much acceleration will it have? It will clearly depend on both the object’s mass and on the amount of force. Experiments with any particular object show that its acceleration is directly proportional to the total force applied to it. This may seem wrong, since we know of many cases where small amounts of force fail to move an object at all, and larger forces get it going. This apparent failure of proportionality actually results from forgetting that there is a frictional force in addition to the force we apply to move the object. The object’s acceleration is exactly proportional to the total force on it, not to any individual force on it. In the absence of friction, even a very tiny force can slowly change the velocity of a very massive object. Experiments also show that the acceleration is inversely proportional to the object’s mass, and combining these two proportionalities gives the following way of predicting the acceleration of any object: Newton’s second law: a = Ftotal / m, where m is an object’s mass, Ftotal is the sum of the forces acting on it, and a is the acceleration of the object’s center of mass. The case is presently restricted to where the forces of interest are parallel to the direction of motion. For example: A bus with a mass of 2000 kg accelerates from 0 to 25 m/s (freeway speed) in 34 s. Assuming the acceleration is constant, what is the total force on the bus? We solve Newton’s second law for Ftotal = ma, and substitute a = v/t for a, giving Ftotal = mv/t = (2000 kg)(25 m/s – 0 m/s)/(34 s) = 1.5 kN.
As with the first law, the second law can be easily generalized to include a much larger class of interesting situations: suppose an object is being acted on by two sets of forces, one set lying along the object’s initial direction of motion and another set acting along a perpendicular line. If the forces perpendicular to the initial direction of motion cancel out, then the object accelerates along its original line of motion according to a = Ftotal / m. (1916) Text 1C. Newton’s Third Law Read, translate the text and answer the question: Was Newton’s Third Law ever violated? Newton created the modern concept of force starting from his insight that all the effects that govern motion are interactions between two objects: unlike the Aristotelian theory, Newtonian physics has no phenomena in which an object changes its own motion. Is one object always the “order-giver” and the other the “order-follower”? As an example, consider a batter hitting a baseball. The bat definitely exerts a large force on the ball, because the ball accelerates drastically. But it is known that the ball also makes a force on the bat. How does the ball’s force on the bat compare with the bat’s force on the ball? The bat’s acceleration is not as spectacular as the ball’s, since the bat’s mass is much greater. In fact, careful measurements of both objects’ masses and accelerations would show that mballaball is very nearly equal to mbatabat, which suggests that the ball’s force on the bat is of the same magnitude as the bat’s force on the ball, but in the opposite direction. Let’s discuss two examples: a) Two magnets exert forces on each other; b) Two people’s hands exert forces on each other. In the first experiment, a large magnet and a small magnet are weighed separately, and then one magnet is hung from the pan of
the top balance so that it is directly above the other magnet. There is an attraction between the two magnets, causing the reading on the top scale to increase and the reading on the bottom scale to decrease. The large magnet is more “powerful” in the sense that it can pick up a heavier paperclip from the same distance, so many people have a strong expectation that one scale’s reading will change by a far different amount than the other. Instead, the two changes are found to be equal in magnitude but opposite in direction: the force of the bottom magnet pulling down on the top one has the same strength as the force of the top one pulling up on the bottom one. In the second experiment, two people pull on two spring scales. Regardless of who tries to pull harder, the two forces as measured on the spring scales are equal. Interposing the two spring scales is necessary in order to measure the forces, but the outcome is not some artificial result of the scales’ interactions with each other. If one person slaps another hard on the hand, the slapper’s hand hurts just as much as the slappee’s, and it doesn’t matter if the recipient of the slap tries to be inactive. (Punching someone in the mouth causes just as much force on the fist as on the lips. It’s just that the lips are more delicate. The forces are equal, but not the levels of pain and injury.) Newton, after observing a series of results such as these, decided that there must be a fundamental law of nature at work: Newton’s third law: Forces occur in equal and opposite pairs: whenever object A exerts a force on object B, object B must also be exerting a force on object A. The two forces are equal in magnitude and opposite in direction. In one-dimensional situations, we can use plus and minus signs to indicate the directions of forces, and Newton’s third law can be written succinctly as FA on B = –FB on A. There is no cause and effect relationship between the two forces. There is no “original” force, and neither one is a response to the other. The pair of forces is a relationship. Newton came up with the third law as a generalization about all the types of forces
with which he was familiar, such as frictional and gravitational forces. When later physicists discovered a new type force, such as the force that holds atomic nuclei together, they had to check whether it obeyed Newton’s third law. So far, no violation of the third law has ever been discovered, whereas the first and second laws were shown to have limitations by Einstein and the pioneers of atomic physics. Newton’s third law does not mean that forces always cancel out so that nothing can ever move. If the two figure skaters, initially at rest, push against each other, they will both move. It often sounds as though Newton’s third law implies nothing could ever change its motion, since the two equal and opposite forces would always cancel. The two forces, however, are always on two different objects, so it doesn’t make sense to add them in the first place — we only add forces that are acting on the same object. If two objects are interacting via a force and no other forces are involved, then both objects will accelerate — in opposite directions! It doesn’t make sense to refer to the equal and opposite forces of Newton’s third law as canceling. It only makes sense to add up forces that are acting on the same object, whereas two forces related to each other by Newton’s third law are always acting on two different objects. Newton’s third law is completely symmetric in the sense that neither force constitutes a delayed response to the other. Newton’s third law does not even mention time, and the forces are supposed to agree at any given instant. This creates an interesting situation when it comes to non contact forces. Suppose two people are holding magnets, and when one person waves or wiggles her magnet, the other person feels an effect on his. In this way they can send signals to each other from opposite sides of a wall, and if Newton’s third law is correct, it would seem that the signals are transmitted instantly, with no time lag. The signals are indeed transmitted quite quickly, but experiments with electronically controlled magnets show that the signals do not