Книга / 02 Unit 02

Unit 2

Grammar: Past Participle, Simple Tenses (Passive Voice); Pronouns: demonstra- tive, personal and possessive.

Reading Exercises

1. Read the following words:

[e] [ǽ] [ ei ] [I ] [ άi] [ Λ ]

ten lamp skate pin drive must

pen flag brave tip wide bulb

rest that wave silk size dusk

nest hand take lift life rust

get stamp plate nil type run

2. Practise reading the two-syllable words with the stress on the first syllable:

habit, chemist, volume, logic, planet, limit, value, civil, solid, critic, open.

3. Practise reading the many-syllable words with the stress on the second syllable: develop, deposit, examine, consider, deliver, determine, remember, prohibit, establish, historic, elastic.

4. Practise reading the words with double stress:

perpendicular, exploitation, education, periodical, consultation, composition, exploration, experimentation, electronic, divisibility, contradiction, communication.

TEXT 2 A

Potential and Kinetic Energy

The capacity of a body to perform work is called its energy. This energy is designated potential if it is due to the position of the body. But a moving body can also do work. Energy in this form is designated as kinetic.

If a body is allowed to fall freely, its rate of descent steadily increases, and it attains its maximum velocity just as it reaches the ground. At this point the body possesses no potential energy at all, for its distance above the ground is zero, but it does have kinetic energy because of its motion. Evidently energy of position is converted into energy of motion.

Potential energy is usually not difficult to measure: it is the product of the resistance and the distance covered.

But how can we determine the kinetic energy, or work-performing capacity, of a moving body from knowledge of its weight and velocity?

Imagine that a moving body of mass m and velocity V strikes against an obstacle and is brought to rest. The change of velocity is the difference between the original and the final velocity; it is numerically equal to V, for the final velocity is zero. Acceleration equals the change of velocity divided by the time required for its accomplishment: i.e. acceleration = V/t. But we know that the force exerted on (or by) any body is its acceleration (rate of change of velocity) multiplied by the mass which undergoes this change. In this case the force exerted by the body must be equal to mass acceleration

F = m V/t

(to be read: equals m multiplied by V divided by t)

The work done is the force exerted multiplied by the distance through which it acts; but distance S equals average velocity

(i.e. (Original velocity + final velocity/2) t)

so S = (V + O/2) t = (v/2) t

Now W = F S

In this equation we shall substitute the equivalent values of F and S as found in the preceding paragraph, and also replace work by kinetic energy(KE), for we are really considering the work-accomplishing capacity of the moving body.

Hence KE = mV/t Vt/2 = 1/2mV²

(to be read: the kinetic energy of a moving body is equal to one-half the product of its mass and the square of its velocity).

While this equation is familiar enough, its derivation is not always understood, and the reasoning given here is one of the easier ways of appreciating its logical grounding.

Answer the questions:

1. What is called energy?

2. What energy is designated as kinetic?

3. When does a body possess no potential energy at all?

4. Why does a body possess no potential energy when it reaches the ground?

5. How can the change of velocity be determined?

6. What is acceleration?

7. What values are to be substituted for determining kinetic energy?

Exercises

1. Translate the following worlds paying attention to the suffixes:

-ful useful, beautiful, wonderful, powerful, peaceful

-less useless, careless, aimless, powerless

-able attainable, changeable, valuable, probable, reasonable

-ty capacity, possibility, safety, speciality

-ly freely, steadily, originally, finally, really, considerably, easily, quickly, slowly, rapidly, freely.

2. Translate the following worlds with the prefix “over”:

to overact, to overbuild, to overcharge to overflow, to overheat, to overload, to overproduce, to overweight, to overwork, to overcome.

3. Fill in the blanks with the words given below:

Equal, unequal, to be equal to, to equal, equality, equation.

1. The values measured proved to be … .

2. Potential energy is … to the resistance multiplied by the distance covered.

3. The derivation of this … presents some difficulty in understanding.

4. These two bodies are of … weight.

5. Average velocity … one half the sum of original and final velocity.

6. This is the ... representing the relationship between distance of descent and time of descent.

7. The … of the amounts of potential and kinetic energy in the same body is quite evident.

8. The … derived proved the … of these two values.

9. One form of energy is converted into another, their amounts are … .

4. Translate into English using Passive Voice:

1. Цим рiвняням часто користуються.

2. На нього часто посилаються.

3. Цю величину треба прийняти до уваги.

4. Для виведення рiвняння кiнетичноi енергii визначають величину сили i вiдстанi.

5. Потенцiальна енергiя вимiрюється як добуток опору, який треба подолати, i вiдстанi.

6. За рiвнянням сили i вiдстанi наведено рiвняння кiнетичноi енергii.

5. Translate the following word-combinations:

the position of a body; to perform work; to fall freely; the rate of descent; to attain its maximum velocity; to reach the ground; the product of the resistance overcome and the distance covered; work-performing capacity; strike against an obstacle to be brought to rest; the force exerted on any body; work-accomplishing capacity.

6. Make up pairs of the following words and translate them into Ukrainian:

1)moving a)velocity

2)maximum b)capacity

3)resistance c)values

4)work-performing d)energy

5)equivalent e) grounding

6)kinetic f)covered

7)logical g)body

8)distance h)overcome

7. Make up questions to the following answers:

1. When force is exerted through any distance, work is performed. 2. The measure of the work accomplished is the product of the resistance of force multiplied by the distance. 3. The energy of position is called potential. 4. On the ground the potential energy of the body is reduced to zero and its kinetic energy reaches its possible maximum. 5. To define force the value of mass which undergoes the change should be determined. 6. The law discovered showed that energy is converted from one form into another in equal amounts.

8. Transform the sentences using Passive Voice where it is possible:

Suppose that we place a body on a shelf. It has the capacity to perform work. If we attach this body to another one of equal weight and allow it to fall freely, the body will descend to the ground and its rate will steadily increase. In doing so, it will lift the other body up to the level of the shelf. When the falling body reaches the ground, the process of converting potential energy into kinetic energy evidently comes to an end.

TEXT 2 B

Energy

Translate the text using a dictionary

Man’s entire life is linked with energy. We need more energy with each passing year. Energy was, is and will remain the foundation of economy, of the development of civilization. That’s why energy problems are now among the most important problems that cause concern of the whole of mankind.

What is energy? What are its forms and sources? How is mankind’s ever growing need for energy to be satisfied?

The capacity for doing work is called energy. A body possesses energy when due to its position or condition it is capable of doing work, and the work it can do is a measure of its energy.

As we know, energy is of two types: potential or kinetic. Potential energy is the energy that has been stored by a body within it. A body possesses potential energy thanks to its position or condition. All fuels (coal, oil, gas, etc.) contain chemical potential energy because they produce the heat that will bring to motion modern engines and do physical work of great importance for our modern industrial world.

Water in a dam is a good example of potential (stored up) energy as well. It possesses this energy because of its higher position. When water is falling with great speed it turns huge turbine wheels and supplies them with kinetic energy. The motion of the turbine can now produce electric energy, which will be transmitted to distant homes and factories. Here electric devices are serving man in a thousand of ways.

Thus, kinetic energy is the energy that a body has due to motion. The potential energy of the weight in its highest position is the same as its kinetic energy after it has fallen under the action of gravity to its lowest position. It may be very large, as the motion of the earth, or very small as that of molecules or even electrified particles.