UNIT 8

 

II. Read the text. Use a dictionary, if necessary.

 

Text: “Dynamics. Laws of Motion”.

 

Dynamics is the study of the ways in which objects behave when they are acted on by forces. Such forces are all around us – for example, the gravitational force acting on a falling object, the air resistance that offsets the full effect of gravity on it, and the frictional force that makes it difficult to drag an object along the ground.

Just as there are many different types of forces, there are also different types of motion produced by those forces. In linear motion, an object moves in a straight line and a falling body is an example. Circular motion is produced when an object is acted on by a force that originates from a central point. If an object is held in equilibrium by two forces, and the extra force resulting from slightly moving the object from its equilibrium position is directly proportional to the distance moved, then the object oscillates regularly in simple harmonic motion.

For an understanding of dynamics, it is necessary to have a knowledge of kinematics, which is the study of motion alone, without taking into account what causes the motion. The most basic concept in kinematics is that of the displacement of a particle; this is the length and direction of the line along which the particle moves from some fixed point, the origin. A quantity, in which both magnitude and direction are specified, is called a vector. And vectors are of great importance in physics.

The next concept is that of the velocity of the particle. It is defined as the rate of change of the displacement with time. Velocity is itself a vector. The commonly-used word speed is reserved by physicists to denote only the magnitude of an object’s velocity, but not its direction. Any quantity that measures only the magnitude of some phenomenon and not its direction as well is known as a scalar quantity. Multiplying the velocity of an object by its mass gives us another vector quantity – momentum.

When the velocity of an object changes, it either accelerates or decelerates. The rate of change of velocity with time is measured in meters per second per second (ms^-2) or an equivalent unit such as kilometers per hour per hour (km hr^-2). Acceleration itself can vary with time.

The fundamental problem of dynamics is determining the motion of an object acted on by forces. The three basic laws governing this behaviour are called Newton’s laws of motion, after the English mathematician and physicist Isaac Newton (1642-1727), who formulated them in the seventeenth century, along with the law of universal gravitation.

Newton’s first law of motion states that an object will remain at rest or will continue to move uniformly in a straight line at constant velocity unless acted on by a force.

Newton’s second law goes a stage further to describe how an object behaves when a force does act on it. This law states that the rate of change of momentum of an object is proportional to the force acting on it.

Newton’s third law of motion concerns the interaction of forces produced by objects. It states that if one object exerts a force on another, that second object exerts an equal and opposite force on the first. This is the principle of action and reaction. A common example of this principle in operation occurs when someone tries to step onto land from a boat. In getting out of the boat, the person exerts a force on it. So as he goes forward onto land, the boat is pushed in the other direction.

 

III. Form adverbs from adjectives by adding the suffix – ly and translate them.

 

Different, straight, central, slight, direct, proportional, regular, simple, harmonic, basic, great, common, fundamental, universal, uniform, constant, necessary, original.

 

IV. Practice the following speech pattern.

 

Pattern 1.  For an understanding of dynamics, it is necessary to have a knowledge of kinematics.

 

 

V. Find the sentences that can’t be found in the text.

 

1. Just as there are many different types of forces, there are also different types of motion produced by those forces.
2. The most basic concept in kinematics is that of the displacement of a particle.
3. The three basic laws governing this behaviour are called Newton’s laws of motion.
4. Using Newton’s laws it is possible to find the position of a body by a knowledge of the relation between that position and its velocity or rate of change of velocity at any other time.
5. The calculus, developed by Newton, could be used and was used by him for solving a great variety of mechanical and hydrodynamic problems.
6. The object of Newton was to demonstrate how universal gravity could maintain the system of the world.
7. Newton established, once and for all, the dynamic view of the universe instead of the static one and showed that the universe was regulated by simple mathematical laws.

 

VI. Put the following sentences in the right order.

 

1. When the velocity of an object changes, it either accelerates or decelerates.
2. For an understanding of dynamics, it is necessary to have a knowledge of kinematics, which is the study of motion alone.
3. Dynamics is the study of the ways in which objects behave when they are acted on by forces.
4. The fundamental problem of dynamics is determining the motion of an object acted on by forces.
5. Just as there are many different types of forces, there are also different types of motion produced by those forces: linear motion, circular motion, simple harmonic motion.
6. The next concept is that of the velocity of the particle.
7. The most basic concept in kinematics is that of the displacement of a particle.

 

VII. Find English equivalents in the text.

 

1. когда они подвергаются воздействию со стороны сил _____________
2. компенсировать воздействие гравитации ________________________
3. удерживаться в положении равновесия __________________________
4. прямо пропорционально _______________________________________
5. длина и направление линии ____________________________________
6. обозначать только величину ___________________________________
7. векторная величина ___________________________________________
8. скалярная величина ___________________________________________
9. умножение ____________________________________________________
10. измеряется в __________________________________________________
11. основные законы ______________________________________________
12. с постоянной скоростью _______________________________________
13. закон гласит _________________________________________________
14. равная и противоположно направленная сила __________________
15. закон действия и противодействия _____________________________

 

VIII. Find Russian equivalents to the following expressions in the text.

 

1. the ways in which objects behave __________________________________
2. the gravitational force ___________________________________________
3. air resistance __________________________________________________
4. frictional force _________________________________________________
5. linear motion __________________________________________________
6. circular motion ________________________________________________
7. a force that originates from a central point ___________________________
8. the extra force resulting from _____________________________________
9. equilibrium position _____________________________________________
10. the distance moved ______________________________________________
11. causes the motion _______________________________________________
12. the displacement of a particle ______________________________________
13. quantity _______________________________________________________
14. magnitude _____________________________________________________
15. momentum ____________________________________________________
16. can vary with time ______________________________________________
17. the law of universal gravitation ____________________________________
18. to move uniformly in a straight line _________________________________
19. exerts a force on another object ____________________________________

 

IX. Analyze the structure of the sentences.

 

1. If an object is held in equilibrium by two forces, and the extra force resulting from slightly moving the object from its equilibrium position is directly proportional to the distance moved, then the object oscillates regularly in simple harmonic motion.
2. Multiplying the velocity of an object by its mass gives us another vector quantity – momentum.
3. Newton’s second law goes a stage further to describe how an object behaves when a force does act on it.

 

X. Fill in the missing words.

 

1. ________ is the study of the ways in which objects behave when they are acted on by forces.
2. Such forces are all around us – for example, the ________ force acting on a falling object, the _________ ____ that offsets the full effect of gravity on it, and the ________ force.
3. In _______ _______ an object moves in a straight line.
4. For an understanding of dynamics, it is necessary to have a knowledge of _____ which is the study of motion alone.
5. The most basic concept in kinematics is that of the ________ of a particle.
6. Such a quantity in which both ______ and ________ are specified, is called a vector.
7. ________ the velocity of an object by its mass gives us another vector quantity - ________.
8. When the velocity of an object changes, it either _______ or _______.
9. The fundamental problem of dynamics is ________ the motion of an object acted on by forces.
10. The three basic laws ________ this behaviour are called laws of motion.
11. Newton’s first law of motion _____ that an object will remain at rest or will continue to move ________ in a straight line at a constant velocity.
12. Newton’s second law states that the rate change momentum an object is proportional ______ the force acting ______ it.
13. Newton’s third law _______ motion concerns the interaction _____ forces produced ________ objects.
14. This is the principle ________ action and reaction.

 

XI. Fill in the prepositions if necessary.

 

1. Dynamics is the study ___ the ways ___ which objects behave when they are acted ___ ___ forces.
2. The air resistance offsets the full effect ___ gravity ___ a falling object.
3. There are different types ___ motion produced ___ the forces.
4. If an object is held ___ equilibrium ___ two forces, the extra force is directly proportional ___ the distance moved.
5. ___ an understanding ___ dynamics, it is necessary to have a knowledge ___ kinematics.
6. Kinematics is the study ___ motion alone, ___ taking into account what causes the motion.
7. The velocity ___ the particle is the rate ___ change ___ the displacement ___ time.
8. Multiplying the velocity ___ an object ___ its mass gives us momentum.
9. Acceleration can vary ___ time.
10. Newton formulated his laws ___ motion ___ the seventeenth century, ___ ___ the law ___ universal gravitation.
11. ___ getting ___ ___ the boat, the person exerts a force ___ it.
12. So the boat is pushed ___ the other direction.

 

XII. Define whether the sentences are true or false.

 

1. Dynamics is the study of the ways in which objects behave when they are acted on by forces.
2. There are many different types of forces but there are only two types of motion produced by those forces.
3. Linear motion is produced when an object is acted on by a force that originates from a central point.
4. Such a quantity, in which both magnitude and direction are specified is called a vector.
5. The velocity of the particle is defined as the rate of change of the displacement with temperature.
6. Multiplying the velocity of an object by its mass gives us another vector quantity – momentum.
7. The first law of motion states that an object will remain at rest or will continue to move uniformly in a straight line at variable velocity unless acted on by a force.
8. The second law states that the rate of change of momentum of an object is proportional to the force acting on it.
9. The third law states that if one object exerts a force on another, that second object exerts an equal and opposite force on the first. 

 

XIII. Practice with someone asking and answering.

 

1. What is dynamics?
2. What are the forces that act on objects?
3. Are there many different types of motion produced by the forces?
4. What happens in linear motion?
5. When is circular motion produced?
6. What is kinematics?
7. What is the most basic concept in kinematics?
8. What is the displacement of a particle?
9. What is called “a vector”?
10. What quantity is called “a scalar”?
11. What gives us momentum?
12. What happens when the velocity of an object changes?
13. What is the fundamental problem of dynamics?
14. How are the three basic laws of dynamics called?
15. What does Newton’s first law of motion state?
16. What does Newton’s second law describe?
17. What does Newton’s third law of motion concern?

 

XIV. Put questions to the following sentences.

 

1. Air resistance offsets the full effect of gravity on a falling object.
2. An object is held in equilibrium by two forces.
3. Newton formulated his laws of motion in the seventeenth century.

 

XV. Dictate the following sentences in English to your fellow-students. Check them together.

 

1. Dynamics is the study of the ways in which objects behave when they are acted on by forces.
2. For an understanding of dynamics, it is necessary to have a knowledge of kinematics.
3. The most basic concept in kinematics is that of the displacement of a particle.
4. The three basic laws governing the behaviour of objects are called Newton’s laws of motion.

 

XVI. Dictation-translation.

 

1. При прямолинейном движении тело движется по прямой линии - падающее тело является примером.
2. Для понимания динамики, необходимо иметь представление о кинематике, которая изучает исключительно движение, не принимаяво внимание факторы, которые вызывают движение.
3. Самое главное понятие в кинематике - это «смещение материальной точки», т.е. длина и направление линии, вдоль которой движется частица от какой-то фиксированной точки - начала координат.
4. Величина, в которой учитывается как численное значение, так и направление, называется вектором.
5. Скорость частицы можно определить как темп изменения перемещения частицы со временем.
6. Любая величина, которая измеряет только численное значение частицы, но не ее направление, называется скалярной величиной.
7. Умножение скорости тела на его массу дает нам очень важную векторную величину - импульс.
8. Три основных закона называются законами движения Ньютона, который сформулировал их в 17 веке, вместе с законом всемирного тяготения.
9. Первый закон движения гласит, что тело будет оставаться в состоянии покоя или будет продолжать равномерное движение по прямой (линии) с постоянной скоростью, если не подвергается воздействию со стороны.
10. Второй закон движения гласит, что скорость изменения импульса тела прямо пропорциональна силе, действующей на него.
11. Третий закон движения гласит, что если одно тело оказывает воздействие на второе тело, то второе тело воздействует с равной и противоположно направленной силой на первое.