III. Scan the text to find answers to these questions.

1. How did primitive man get the energy he needed?

2. How much energy does man consume today?

3. What does technological man do half of his Iife7

4. In what two ways is energy used?

5. What is the standard measurement of energy cost?

6. Does the car require much energy?

7. Why is it essential to cut energy consumption?

8. What is the primary source of energy?

Read and translate.

Forms of energy

Energy is the ability to do work. When a hammer strikes a nail it exerts a force on the nail that causes it to move. The movement of the hammer has the ability to do work and therefore has a form of energy that we call kinetic energy. Kinetic energy is the energy of motion. Or the energy of a moving body. The equation of kinetic energy is E = 112 m V². (E is equal to a half of m multiplied by V squared or V to the second power).

An object may have energy not only because of its motion but also because of its position or shape. For example, when a watch spring is wound, it is storing energy. When this energy is released, it will do the work of moving the hands of the watch. This form of energy is called potential energy. Potential energy is stored energy. Water in a dam is another example of potential energy.

A lifted weight possesses potential energy due to it's position. It is capable of doing work as it falls under the action of gravity. The potential energy of в lifted body with respect to a given level is E = mgh. (E is equal to mg by h).

There are many types of kinetic and potential energy, including chemical, thermal, mechanical, electrical and nuclear energy.

Energy can be transformed or changed from one type to another. For example, an apple hanging on a tree has potential energy, or the energy of position. As it falls, it loses potential energy because its height decreases. At the same time, it acquires kinetic energy, or the energy of motion, because its velocity increases. Potential energy is being transformed, into kinetic energy.

Frequently, the transfer of energy involves a transfer from one body to another. When you lift up a rock, you are changing the chemical energy of the food you have eaten into muscle energy. As you lift the rock high, your muscle energy is changing into the rock's potential energy.

When energy is transformed from one type to another or transferred from one body to another no energy is lost. When we measure energy, we discover that the total amount remains intact. Let's assume we prepared, cooked, and then ate some food. If we measure carefully all the energy that remains at the end of this process (such as potential, kinetic and heat), we would always find exactly the same amount of energy as we started with (such as chemical and potential). Energy can thus be converted from one form to another but never created or destroyed. This is called the law of the conservation of energy.

Matter, like energy, can be converted from one form to another but nei­ther be created nor destroyed. In 1785, the French chemist Antoine Lavoisier demonstrated that there is no gain or loss of mass in a chemical change. For example, when a piece of wood is burned, ashes remain. At the same time, the wood combines with oxygen in the air to form carbon dioxide and water vapour, which pass into the air. If the carbon dioxide, water vapor, and ashes are added together, the total weight will equal the original weight of the wood plus the oxygen in the air. Thus, there is no change in the total mass. This is called the law of the conservation of mass.

Ex. I. Find the equivalents:

the energy possessed изолированная система

a lifted weight по отношению

an isolated system энергия, присущая

with respect to данное тело

the given body поднятый груз

a watch spring данный уровень

stored energy стрелки часов

given level плотина

hands of the watch часовая пружина

dam сохраняемая энергия

aquired energy энергия мускулов

muscle energy приобретенная энергия

Ex. II. a) Join suitable parts:

The potential energy of a body is the energy...

a)... done upon it to bring it into motion.

b)... lifted weight to the given level.

c)... possessed by the body thanks to its position.

d)... fallen under the action of gravity.

b) Find the answer to the following question:

What is the kinetic energy?

1. It is the energy possessed by the body thanks to its position or con- i figuration. 2. It is the energy converted from heat energy by means of machines. 3. It is the energy received by combusting coal or oil. 4. It is the energy of a moving body expressed in terms of its mass m and its velocity V.

Ex. III. Insert prepositions wherever necessary:

I. The movement.... a hammer has the ability to do work 2. Energy can , be transformed ... one type... another. 3. A lifted weight is capable ...doing work as it falls ...the action ..gravity. 4. The energy ...a lifted body ...respect...a given level is potential energy. 5. V may be read V ...the second power. 6.... example, when a piece ...wood is burnt, ashes ran an.

Ex. IV. Translate from Russian into English;

1. Силы, действующие на тело, производят работу. 2.Тело, обладающее потенциальной энергией, может совершать работу. 3. Студент, читающий этот текст, учится в нашей группе. 4, Студенты, решающие это уравнение, со второго курса. 5. Кинетическая энергия, которой обладает тело, зависит от его массы. 6. Совершенная работа может быть измерена разными способами. 7. Измеряемое расстояние будет обозначено на схеме. 8. Используемое оборудование было получено в прошлом году. 9. Производимое оборудование широко используется на многих заводах. 10. Использованное оборудование оказалось очень хорошим. П. Приложенная сила перевела тело из состояния покоя в состояние движения.

Ex. V. Read the text in 3 minutes without a dictionary and title it:

A lifted weight has potential energy due to the higher position into which it has been lifted since it can do work as it falls under the action of gravity. Since energy may be transformed from potential to kinetic, a lifted weight which possesses potential energy in its highest position if allowed to fall will gradually lose I (s potential .energy. At the same time it will acquire velocity and therefore kinetic energy. A ball thrown vertically into the air possesses at the beginning of its flight kinetic energy, but as it rises it gradually comes to rest thus losing its energy in that form. However, as it rises it is acquiring potential energy with respect to the level from which it started. In other words while rising its kinetic energy is transformed into potential one. It is found that the total energy possessed by the body or system of bodies under consideration before and after the transformation is the same

Ex. VI. Work in pairs.

Find out: if a lifted body possesses kinetic energy.

Pattern: St. A.: A lifted body doesn't possess kinetic energy, does it? St. В.: No, it doesn't, it possesses potential energy.

1. your partner knows two forms of energy; 2. (s)he learnt them at school; 3. all forms of energy will be studied at the institute; (change roles); 4. (s)he made any experiments in school; 5. (s)he will make more experiments at the institute; 6. (s)he likes to make experiments.

Ex. VII. Translate the following sentences paying attention to the words in bold type:

1, Our country gained the victory in the Great Patriotic war. 2. What is the time now?-Half past three (3.30).- No, it is only a quarter past three (3.15), your watch gains IS minutes. 3. In the summer camps most children usually gain I or2kgs. 4. If you go thereby the underground, it will take you only 15 minutes instead of 25 by bus, it means you will gain 10 minutes. 5. A little weight has potential energy since it can do work as it falls under the action of gravity. 8. The scientists weighed the tested piece of metal and compared its weight with untested ones.

Ex. VIII. Correct the following wrong statements in not less than 3 sentences:

1. The kinetic energy of a body is the energy possessed by the body thanks to its position or configuration.

2. The body possesses kinetic energy if it is lifted to some height.

3. The potential energy of a moving body may be expressed in terms of its mass m and its velocity V.

Ex. IX. Solve the following problems:

1. What is the potential energy of a ball weighing 1 kg (0,5 kg; 2 kg) raised through 3 m (2 m, 5 m) vertically?

2. Calculate the kinetic energy of a bullet weighing 100 gr. and travel­ling at 350 m/sec.

3. What is the kinetic energy of a car travelling at 70 km/hour the mass of which is 2 tons?

4. Prove that the potential energy of a body which has fallen to the ground is equal to 0.

Read the article carefully for the details about the energy problems. Give a title to the article.

Energy is an essential part of our civilization. A million years ago primitive man used only 6,000 (kJ) a day, which he got from the food he ate. A hundred thousand years ago people had learnt to make fire and used four times as much energy (the equivalent of 25,000 kJ). By the 15th century man using animals, windmills and waterwheels, and a little coal, was already consuming nearly twenty times as much energy (120,000 kJ), By 1875 the steam engine made 340,000 kJ a day available to industrial man in England. Today's technological man uses 1,000,000 kJ a day, or one hundred and fifty times as much as primitive man, about one third in the form of electricity.

Why is our energy consumption constantly increasing and acce­lerating? The reasons are evident. Technological man lives four times* as long as primitive man and twice as long as man in the 15th century. Nearly half of man's life today is spent on educating himself, leisure and creative activities. Medieval man spent only a quarter of his thirty-five years in these pursuits,, and primitive man only one sixth in his short life of eighteen years. What do we need energy for? Comfort and lighter work, first of all. Energy consumed in great quantities falls into two kinds: a) energy needed every day (lighting, heating, etc.) and b) energy used to produce necessary objects (house, clothes, etc.). Take a man building a small house (10 tons of oil-equivalent), heating (3 tons of oil-equivalent) and lighting (200 kg of oil-equivalent or 700 kWh) it for a year and having a car (1.3 tons of oil-equivalent + 1.3 tons for every 12,000 km run). The energy cost of these basic things is tremendous but multiply it by 6 billion to get the real picture of man's needs. Besides, energy consumption is sure to increase since the more energy is consumed, the easier our life becomes.

The current energy problem caused by many interrelated factors I 'must be tackled quickly. Strange as it sounds, there is no shortage of primary energy. The sun provides ten thousand times as much energy as we require today, in many forms ranging from solar radiation through wind and waves to trees and plants. The problem is to convert these resources into mechanical work or other usable forms of energy. The history of energy has been the history of converters - man's body itself converting food into warmth and mechanical work, animals doing such work more powerfully, the waterwheel, the windmill, the steam engine, the nuclear reactor and in the near future, the solar cell.

Additional texts.