Exercises

1. Listen, read and translate the text.

2. Answer /he following questions in a written form.

1. What force does a bar magnet exert? 2. When is work done? 3. What may force produce? 4. How may machines be classified? 5. How is power defined? 6. How do you define energy? 7. What the most important forms of energy do you know?

3. Make up and write 8 sentences using the words given in the table:

40

The students They A train A force He

Solves is doing performs is explaining are performing is acting over make

experiments a new pheno-mena new problems work a body

very often. every les­son. now.

4. Substitute the infinitive by the proper form of the verb (active or passive):

1. The units in which energy (to measure) depend on the type of energy concerned. 2. We (to measure) heat energy in calories. 3. Me-chanical energy (to measure) in joules. 4. Scientists (to measure) electrical energy in joules. 5. A kilo­watt-hour (to be) the energy in 1 hour when the rate of working (to be) 1 kilowatt. 6. Of all these forms of energy, heat (to be) probably the most important, for all other forms eventually (to finish) up as heat.

5. Make up and write 8 questions using the words given in the table:

Who What When Where

is does do are

a teacher he a train a force work the students

explain reading doing solving move making done study

a book a rule work a body an experiment problems

6. Copy these sentences putting "rest", "motion", "force", "energy", "work", "exert", "slows" in the blanks:

1. When we are speaking of ..., lime is taken into ac­count. 2. The ability to do work is called ... . 3. A change from a state of ... to a state of ... is connected with the ap­plication of ... , 4. The brakes of a motor-car ... a force which ... up the car. ... is done when a force is acting over a dis­tance.

7. Explain the use of the Present Indefinite and Present Continuous Tenses and translate these sentences into Russian :

1. We are standing near an atomic installation. 2. Do you know how it operates? 3. What is taking place when is set in motion? 4. The fuel is burning in it. 5. You know that when fuel burns, heat is produced. 6. In the boiler there is water which is boiling due to the heat of fuel. 7. The boil ing water is changing into steam and the pressure of the steam is driving the steam engine.

8. Make up and write all possible questions to these sen fences:

1. Whenever work is done, energy of some other form is used up. 2. In fact, scientists regard work itself as a form of energy. 3. The total amount of energy in the universe is a constant; and if any energy disappears in one form, it re­appears in another without loss.

Laboratory Exercises

9. Listen and practice the pronunciation of the following words:

Language, motion, force, physical, distance, engine, equal; capacity, perform, abound, divide, machine, another, produce, exert; conversation, classified, installation.

10. Listen and repeat in pauses:

A force may move the body from rest. It may change the motion of a body already moving. A force may fail to produce a motion if opposed by another force. Work is done when a force is acting over a distance. The amount of per­formed work is equal to the product of the force by the dis­tance. Power к defined as the rate of doing work. We define energy as capacity to perform work.

11. Listen to these questions on the above text and answer them:

1. What may а force change? 2. What may a force move? 3 What may a force fail to produce? 4. When is work done? 5. How is power defined? 6. How do you define energy?

42

12. Ask questions using the model.

Model: A force causes a body to move.

What does a force cause?

1. A force moves a body. 2. Mechanics deals with the ac­tion of force, 3. A brake exerts a force which slows up the car. 4. The world abounds in energy. 5. The heat energy becomes mechanical energy.

13. Listen to this short dialogue and learn it by heart:

— When work is done, what happens to the energy?

— Let us consider a motor car going on a journey. First, where is any petrol poured into?

— It's poured into the tank.

— That's right. This contains chemical energy. And what contains electrical energy?

— The car battery. Some of the electrical energy is used to overcome friction and to turn the engine.

— You are right. The energy used against friction is liberated as heat.

— What happens to the remainder energy?

— It becomes the energy of motion. The heat energy thus becomes mechanical energy and the car is made to move.

— Thus energy may exist in many forms.

14. Suggested topics for oral narration:

1. Tell about the action of force. Give examples of force.

2. Give the definition of a) work, b) power, c) energy.