POTENTIAL ENERGY

ENERGY

Exercise 1. a). The text you are going to read is headlined “Energy”. Guess what it can run about.

b).Think of 5-7 questions the answers to which you hope to find in the text.

c) In pairs, ask and answer these questions

Exercise 2. Mind the pronunciation of the following words:

measure ['meZq] to require [rI'kwaIq]

ability [q'bIlItI] quantity ['kwPntItI]

science ['saIqns] successive [sqk'sesIv]

weight [weIt] boundary ['baVnd(q)rI]

pulley ['pVlI] collision [kq'lIZ(q)n]

applied [q'plaId] pendulum ['pendjVlqm]

distance ['dIst(q)ns] to recognize ['rekqgnaIz]

to associate [q'sqVSIeIt] capacity [kq'pxsItI]

to exist [Ig'zIst] thermodynamics ["TE:mqVdaI'nxmIks]

to convert [kqn'vE:t] constraint [kqn'streInt]

Exercise 2. Guess the meaning of the following international words:

Energy, kinetic, potential, electrical, chemical, constant, magnetic, mass, total, principle, term, idea, configuration, natural, transformation, process, elastic.

Exercise 3. Choose Russian-English equivalents in the box below.

Exercise 4. The words in A are mentioned in the text “Energy”. Find their definitions in B and translate these words into Russian.

Exercise 5. Find the derivatives of the following words in the text. Pay attention to the suffixes used to form them.

Exercise 6. Match nouns and verbs to form collocations. Use each word once only. Consult the text if necessary.

Exercise 7. There are some words given in italics in the text “Energy”. Choose their synonyms from the box below. The forms of the words in the text may differ from those in the box.

Read the text and fulfill the tasks given in Comprehension check.

ENERGY

The term energy was not applied as a measure of the ability to do work until rather late in the development of the science of mechanics. The idea of energy goes back at least to Galileo in the 17th century.

He recognized that, when a weight is lifted with a pulley system, the applied force multiplied by the distance through which that force must be applied (a product called, by definition, the work) remains constant even though either factor may vary.

Energy is the capacity for doing work. It may exist in many forms. These different forms include potential, kinetic, thermal, electrical, chemical, nuclear, or other various forms. All forms of energy are associated with motion. For example, any given body has kinetic energy if it is in motion. A tensioned device such as a bow or spring, though at rest, has the potential for creating motion; it contains potential energy because of its configuration. Similarly, nuclear energy is potential energy because it results from the configuration of subatomic particles in the nucleus of an atom.

Energy can be converted from one form to another within the constraint of the conservation law. The law of conservation of energy holds for all natural phenomena and requires that the total energy does not change in all changes that occur in nature. The conservation of energy is not a description of any process going on in nature, but rather it is a statement that the quantity called energy remains constant regardless of when it is evaluated or what processes--possibly including transformations of energy from one form into another—go on between successive evaluations.

The law of conservation of energy is applied not only to nature as a whole but to closed or isolated systems within nature as well. Thus, if the boundaries of a system can be defined in such a way that no energy is either added to or removed from the system, then energy must be conserved within that system regardless of the details of the processes going on inside the system boundaries.

The first kind of energy to be recognized was kinetic energy, or energy of motion. In certain particle collisions, called elastic, the sum of the kinetic energy of the particles before collision is equal to the sum of the kinetic energy of the particles after collision. The notion of energy was progressively widened to include other forms. The kinetic energy lost by a body slowing down as it travels upward against the force of gravity was regarded as being converted into potential energy, or stored energy, which in turn is converted back into kinetic energy as the body speeds up during its return to Earth. So the sum of the kinetic and the potential energy of, say, a satellite or a freely swinging pendulum is constant or nearly so. Friction, however, slows down the most carefully constructed mechanisms, thereby dissipating their energy gradually. During the 1840s it was conclusively shown that the notion of energy could be extended to include the heat that friction generates. The truly conserved quantity is the sum of kinetic, potential, and thermal energy. This version of the conservation-of-energy principle, expressed in its most general form, is the first law of thermodynamics. The conception of energy continued to expand to include energy of an electric current, energy stored in an electric or a magnetic field, and energy in fuels and other chemicals.

With the advent of relativity physics (1905), mass was first recognized as equivalent to energy. The total energy of a system of high-speed particles includes not only their rest mass but also the very significant increase in their mass as a consequence of their high speed. After the discovery of relativity, the energy-conservation principle has alternatively been named the conservation of mass-energy or the conservation of total energy.

Notes to the text

Exercise 1. Choose the best ending a, b, or c.

1. The idea of energy dates back to

a) Newton.

b) Galileo.

c) ancient Greek scientists.

2. Energy is

a) the ability to do work.

b) is equal to the product of the applied force and the distance through which that force must be applied.

c) equals mass times one-half of the velocity squared.

3. Energy may exist in

a) two main forms, i.e. kinetic and potential.

b) only if a body moves.

c) different forms that are associated with motion.

4. Energy

a) never changes without losses.

b) can be transformed from one form to another in accordance with the conservation law.

c) of a falling body doesn’t remain constant.

5. The law of conservation of energy

a) states that the total energy does not change in manifold changes that nature undergoes.

b) is applied only to natural phenomena.

c) holds only for bodies at rest.

6. The first form of energy that was recognized by scientists was

a) nuclear energy.

b) potential energy.

c) energy of motion.

7. The kinetic energy lost by a body when it travels upward is converted into

a) thermal energy.

b) potential energy.

c) chemical energy.

8. Mass energy was first recognized

a) when nuclear physics arose.

b) after the discovery of relativity.

c) with the advent of atomic physics.

Exercise 2. Find answers to the following questions.

1. What is energy?

2. When was the term energy used as a measure of the ability to do work?

3. What did Galileo think?

4. What forms of energy do you know?

5. Can energy be converted?

6. What does the law of conservation of energy state?

7. Where is the law of conservation of energy applied?

8. What was the first type of energy to be recognized?

9. When does kinetic energy convert into potential energy?

10. When was heat recognized as a form of energy?

11. What is the truly conserved quantity/

12. What is electrical energy?

13. What happened when relativity physics arose?

Exercise 3. Put the jumbled sentences in the logical order to sum up the contents of the text.

1. The law of conservation of energy is applied to nature as a whole and to closed or isolated systems within nature.

2. Energy is the capacity for doing work.

3. The notion of energy constantly widened to include more and more forms of energy.

4. All these forms of energy are connected with motion.

5. The idea of energy originated in the 17^th century.

6. The energy-conservation principle changed its name to the mass-energy conservation principle.

7. The first kind of energy that was recognized was kinetic energy.

8. The term energy was used as a measure of the ability to do work rather late.

9. There are many forms of energy: potential, kinetic, thermal, electrical, chemical and others.

10. When relativity physics emerged, mass was regarded as equivalent to energy.

11. Energy can be converted from one form into another.

12. The law of conservation of energy requires that the total amount of energy remain constant.

Grammar exercises

Modal verbs: can/could, be able to, may/might. (Meanings expressed by these modal verbs: ability, absence of ability, request, asking for permission, giving permission, refusing permission, reproach).

Exercise 1. Choose the correct alternative.

1. May/Can I record our interview on tape? – Yes, of course you may/can.

2. People heard warnings about the flood, and they could/were able to move out in time.

3. Peter can/may phone in the evening. If he does, ask him to phone later.

4. As soon as I opened the door, I could/might smell gas.

5. Confidential documents may not/cannot be photocopied without prior approval.

6. I thought I was going to miss the plane but I could/was able to get to the airport on time.

7. James broke his leg last summer, so he couldn’t/wasn’t able to play tennis.

8. My appointment was cancelled at the last moment, so I could/was able to go to the fitness centre with my friends.

9. Catherine couldn’t/wasn’t able to speak any Dutch when they moved to the Netherlands last year.

10. I had no key so I couldn’t/wasn’t able to lock the door.

11. When I arrived yesterday everyone was asleep. Fortunately I could/was able to wake my brother and he let me in.

12. Although it was dark, Robin could/was able to find his way through the forest.

13. We could/were able to finish the football match before it started snowing too heavily.

14. Do you want a game? – Sorry, I can’t/am not able to play chess.

15. Look at me, I can’t/am able to ride my bike without any help.

16. When the fire officers arrived they could/were able to put out the flames in a couple of minutes.

17. I knew John had been smoking. I could/was able to smell the cigarettes when I came into the room.

18. He could/was able to untie the ropes without the guards noticing.

19. She looked all over the house, but couldn’t/wasn’t able to find her keys anywhere.

20. I was very busy at work, but I could/was able to have a couple of days off last week.

Exercise 2. Fill in the blanks using can/could, be able to, may/might.

1. In two years you will … speak two foreign languages.

2. The information … be true! I don’t believe you.

3. Last year we … visit Canada.

4. … you help me carry these heavy bags?

5. She is rather old now and … to read without spectacles.

6. She … dance well.

7. Our secretary … to type 100 words a minute.

8. You … at least call her parents.

9. You enter this territory. It is dangerous.

10. I … to meet you at the station yesterday. I was very busy.

11. … I ask you a question, sir?

12. You … not smoke in the corridors.

13. You … do it yourself! It is an easy exercise.

14. … I get down to discussion right now, madam? – Yes, you … .

15. Though I … swim well some years ago, once I … to help a drowning man.

16. The stadium was full of fans, but we … to get tickets for this match.

17. I … to pass my driving test after I have had a few lessons.

18. … I come again? – Yes, you … come at any time you like.

19. She … speak three languages, but she … write any of them when she was younger.

Modal verbs: must, have to, be to, ought to, should. (Meanings expressed by these modal verbs: necessity, duty, obligation, lack of necessity, prohibition, advice, planned action).

Exercise 1. Choose the correct alternative.

1. You mustn’t/don’t have to leave your things unattended.

2. All the payments must/should be made before the goods are delivered.

3. The meeting is to/has to start at 10 sharp tomorrow.

4. As the payment was not made in time, they should/had to break the order.

5. You must/have to take a taxi if you want to catch the next train.

6. I didn’t have to/ mustn’t go to the bank yesterday as I had enough money on me.

7. Students shouldn’t/mustn’t talk at the lectures, they have to/must listen to attentively.

8. Since the new boss took us over, we had to/were to change our methods of work.

9. You’ve got plenty of time. You don’t have to/mustn’t hurry.

10. This book is very valuable. You must/have to handle it carefully.

11. When I was at school we had to/should wear a uniform. Everybody liked it.

12. I like Saturdays because I don’t have to/am not to be in a hurry in the morning.

13. If you feel tired, you should/have to go to bed earlier.

14. You mustn’t/don’t have to invite guests to your hotel rooms.

15. Last night Jack suddenly became ill. We had to/must call the doctor.

16. Your friend is always coughing, he must/has to stop smoking.

17. I don’t have to/mustn’t wear a suit to work, but I usually do.

18. You can tell Tom what I said but he mustn’t/doesn’t have to tell anybody else.

Exercise 2. Fill in the blanks using have to, must, be to, should, ought to.

1. You … bite your nails.

2. Mary, you will … take our dog for a walk.

3. He … to stay at home yesterday because of high temperature.

4. You … tell them the truth.

5. We … to finish the reconstruction according to the signed contract.

6. You … lock the door at night.

7. They … to meet last Friday to discuss important questions.

8. Everyone … obey the law.

9. The bus didn’t come on time, so we … to wait long at the bus stop.

10. You … tell anybody about our meeting. Let’s keep it secret.

11. You … do it at once, otherwise you will let me down.

12. One … look both ways before crossing the street.

13. You … be late. You … to come at 5 o’clock. They will be waiting for you there. – I … to take a taxi to be on time.

14. We … do our homework carefully not to make any mistakes.

15. You … come. There is nothing to do.

16. I don’t think people … get married until they are 21.

Modal verbs can, can’t, must, may/might. (Meanings expressed by these modal verbs: possibility, assumption, doubt, surprise).

Exercise 1. Choose the correct alternative.

1. Do you think the situation may/must change?

2. Can/May he be working out the report?

3. Nothing is so bad but it might/must have been worse.

4. How did they manage to do well last month? – They must/can have increased productivity.

5. He may/can’t have made such a mistake in calculations!

6. Ted didn’t answer the phone so he must/can’t have gone on holiday.

7. Do you think they are all right? They must/can have had an accident or something.

8. What a terrible risk you took – you may/must have been killed!

9. I am waiting for Alice but she might/can’t have forgotten about the meeting.

10. He did everything wrong. He must/can’t have misunderstood you.

11. It is wet outside. It must/may have been raining all the night.

Exercise 2. Fill in the blanks using, must, may/might, can’t.

1. You … be very tired after such a long flight.

2. We … go climbing in the Alps next summer.

3. He … not have arrived yet.

4. You … have told me about that accident earlier!

5. She … be talking seriously!

6. … they have been negotiating the contract for two hours?

7. I am not sure at all but Tom … know about it.

8. Oh no! I cannot find my passport anywhere. - I think it … be in your briefcase or you … have left it at work.

9. His face is red. He … be cold.

10. Wait a minute, the rain … stop soon.

11. … Sally have spent all her money?

12. They … be walking in the park now.

Follow–up activities

Exercise 1. Find in the text “Energy” and read sentences in which

a) the time when the tem energy appeared is indicated;

b) the definition of energy is given;

c) the law of energy is stated;

d) forms of energy are enumerated;

e) possible fields of application of the law of energy conservation are named.

Exercise 2. Use the following key words and word combinations to express the main idea of each paragraph.

1. The idea of energy, to go back to, Galileo.

2. A product, the applied force, the distance, to remain constant, either factor, to vary.

3. Energy, capacity, to do work.

4. To exist, forms of energy.

5. Energy, to convert, forms.

6. The law of conservation, to hold, natural phenomena.

7. The law of conservation, to state, total energy, to change.

8. The law of conservation, to apply, nature, closed systems.

9. The notion of energy, to widen, to include, different forms of energy.

10. The advent, relativity physics, the energy-conservation principle, to name, mass-energy.

Exercise 3. Choose the key sentences from the text “Energy”, write them down omitting less important information. Now work in pairs (or in groups). Ask your groupmate(s) to translate your Russian versions of the key sentences into English. Swap the roles.

Exercise 4. You are a guest speaker at some conferences. You were asked to deliver a report about energy. Use the information from the text and add some more to speak on the problem suggested.

Exercise 5. Watch the video film “Kinetic Energy” and fulfill the tasks to follow.

Task 1. Combine two parts of sentences.

Task. 2. Answer the following questions.

1. What is necessary to make stationary things move?

2. When is work done?

3. Why doesn’t the first billiard ball move

4. Why does this ball start moving?

5. Why can the second ball make the first one move?

6. Where did physicists borrow the English word energy?

7. What does this word mean in Greek?

8. Why does the moving ball have energy?

9. Is work possible without energy?

10. In what units is energy measured?

11. Where does the word kinetic come from? What does this word mean?

Task 3. Put the jumbled sentences in the logical order to sum up the contents of the video film.

1. The first billiard ball doesn’t move because no force acts on it.

2. The English word energy comes from Greek.

3. This energy was transferred to the cue which in turn transferred the energy to the billiard ball by making it move.

4. Stationary things do not move.

5. The second billiard ball makes the first one move as it has movement.

6. If an object has both mass and speed, it has the ability to do work, i.e. to get other things to move.

7. The moving ball had some energy and the origin of this energy was the billiard player whose arm had work in it or energy because of its movement.

8. Physicists decided to call the energy of movement kinetic energy.

9. Force is necessary to make them move.

10. When a force moves an object through some distance, work is done.

Exercise 6. Watch the video film “Potential Energy” and fulfill the tasks to follow.

Task 1. Agree or disagree with the following statements. Give arguments in support of your ideas.

1. Moving things have the ability to do work but they can’t apply a force through a distance.

2. Energy is the capacity for doing work.

3. Work is measured in joules and energy – in newtons.

4. Kinetic energy is the energy of position.

5. Only moving things have energy.

6. Stationary objects possess potential energy.

7. Potential energy can transform into kinetic energy when a stationary object starts moving.

8. kinetic energy can change into potential energy when a moving object comes to a complete stop.

9. After climbing up to the top of the cliff the giant has lost all his energy.

Exercise 2. Arrange the jumbled sentences into the logical order to sum up the contents of the video film.

1. In turn kinetic energy can transform into potential energy when an object stops moving.

2. But they have the energy of position or what physicists call potential energy.

3. The rock on the edge of the cliff has potential energy and no kinetic energy.

4. Moving objects have the ability to do work.

5. Stationary objects can’t have any kinetic energy and they can’t do any work on you.

6. Both work and energy are measured in joules.

7. Not only moving objects have energy.

8. Nevertheless this potential energy can transform into kinetic energy due to the slightest puff of the wind.

9. Thus energy is never lost, one form of it can be transformed into another.

10. The energy of movement is called kinetic energy.

ADDITIONAL TEXTS

Read the texts “Kinetic energy” and “Potential energy’ and translate them in written form.

KINETIC ENERGY

Kinetic energy is a form of energy that an object or a particle has by reason of its motion. If work, which transfers energy, is done on an object by applying a net force, the object speeds up and thereby gains kinetic energy. Kinetic energy is a property of a moving object or particle and depends not only on its motion but also on its mass. The kind of motion may be translation (or motion along a path from one place to another), rotation about an axis, vibration, or any combination of motions.

Translational kinetic energy of a body is equal to one-half the product of its mass, m, and the square of its velocity, v, or 1/2mv.

This formula is valid only for low to relatively high speeds; for extremely high-speed particles it yields values that are too small. When the speed of an object approaches that of light (300000 metres per second, or 186,000 miles per second), its mass increases, and the laws of relativity must be used. Relativistic kinetic energy is equal to the increase in the mass of a particle over that which it has at rest multiplied by the square of the speed of light.

The unit of energy in the metre-kilogram-second system is the joule. A two-kilogram mass moving at a speed of one metre per second has a kinetic energy of one joule.

For a rotating body, the moment of inertia, I, corresponds to mass, and the angular velocity (omega), corresponds to linear, or translational, velocity. Accordingly, rotational kinetic energy is equal to one-half the product of the moment of inertia and the square of the angular velocity, or 1/2I .The total kinetic energy of a body or a system is equal to the sum of the kinetic energies resulting from each type of motion.

POTENTIAL ENERGY

Potential energy is stored energy that depends upon the relative position of various parts of a system. A spring has more potential energy when it is compressed or stretched. A steel ball has more potential energy raised above the ground than it has after falling to the Earth. In the raised position it is capable of doing more work. Potential energy is a property of a system and not of an individual body or particle.

Potential energy arises in systems with parts that exert forces on each other of a magnitude dependent on the relative position of the parts. In the case of the Earth-ball system, the force of gravity between the two depends only on the distance separating them. The work done in separating them farther, or in raising the ball, transfers additional energy to the system, where it is stored as gravitational potential energy.

Potential energy also includes other forms. The energy stored between the plates of a charged capacitor is electrical potential energy. What is commonly known as chemical energy, the capacity of a substance to do work or to evolve heat by undergoing a change of composition, may be regarded as potential energy resulting from the mutual forces among its molecules and atoms. Nuclear energy is also a form of potential energy.

The potential energy of a system of particles depends only on their initial and final configurations; it is independent of the path the particles travel. In the case of the steel ball and the earth, if the initial position of the ball is ground level and the final position is ten feet above the ground, the potential energy is the same, no matter how or by what route the ball was raised. The value of potential energy is arbitrary and relative to the choice of reference point. In the case given above, the system would have twice as much potential energy if the initial position were the bottom of a ten-foot-deep hole.

Gravitational potential energy near the Earth's surface may be computed by multiplying the weight of an object by its distance above the reference point. In bound systems, such as atoms, in which electrons are held by the electric force of attraction to nuclei, the zero reference for potential energy is a distance from the nucleus so great that the electric force is not detectable. In this case, bound electrons have negative potential energy, and those just free of the nucleus and at rest have zero potential energy.

Potential energy may be converted into energy of motion, called kinetic energy, and in turn to other forms such as electrical energy. Thus, water behind a dam flows to lower levels through turbines that turn electric generators, producing electric energy plus some unusable heat energy resulting from turbulence and friction.

Historically, potential energy was included with kinetic energy as a form of mechanical energy so that the total energy in gravitational systems could be calculated as a constant.

Pre-reading tasks

Task 1. The text you are to read is headlined “Mechanical energy”. Below you’ll find named the problems this text could contain. Choose the most appropriate problems to be mentioned in this text:

- definition of mechanical energy;

- description of experiments revealing the existence of mechanical energy;

- names of scientists contributed to the study of mechanical energy;

- forms of mechanical energy;

- facts related to the history of mechanical energy investigations.

After reading the text check whether your choice was correct.

Read the text “Mechanical energy” and fulfill the tasks given below.

Date: 2015-01-12; view: 1685