Text 3 a force, work, energy and power

In the language of science a few words, among them force, work, energy and power, have definite meanings differing a little from the meanings that are often given to them in everyday life.

The word “force” meaning a simple push or pull, is not connected with the idea of time. When forces are pushing upon an object or pulling upon it, they change it from a state of rest to a state of motion or from motion to rest.

Work is done when a force is acting over a distance. In this case, too, the time is not taken into account. For example, work is done when a weight lying on the ground is lifted, when a stone is thrown. However, no work is done in the scientific sense of the word when a man is standing and holding a weight. True, the force is applied, but it results in no work.

The amount of performed work is determined by two factors: the applied force and the distance through which the force acts. In order to calculate the amount of work, the force is multiplied by the distance, that is, the amount of performed work is equal to the product of the force by the distance

Work = Force Distance or W = F S

When we are speaking of power, time is taken into account. Power means the rate at which work is done. It is equal to the work divided by the time which is required to perform it.

Power = Work/Time = (F S)/t

The ability to do work is called energy. There are different kinds of energy: mechanical, chemical, electrical, heat and light energy. All moving bodies, in fact, possess it. For example falling water has a store of energy, for as it is flowing down it can be used to drive the water-wheels of turbines. Coal and other fuels also hold a store of energy. It can be made use of when fuels are being burnt to produce steam .

Notes:

1. A state of rest – стан спокою

2. A state of motion – стан руху

3. To take into account – взяти до відома

Answer the questions:

1. When do forces change an object from a state of rest to a state of motion?

2. When is work done?

3. Is a man performing work when he is standing and holding a weight?

4. What is the amount of performed work determined by?

5. How is the amount of performed work calculated?

6. What is power?

7. What is power equal to?

8. What is energy?

9. Are there different kinds of energy?

10. What are they?

Exercises:

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

1. Operate – operation – operator – operable – operative.

2. Act – action – active – activity.

3. Mechanics – mechanic – mechanical – mechanism – mechanization.

4. Electricity – electric – electrification – electrify – electrician.

5. Industry – industrial – industrialization – industrialist – industrious.

6. Science – scientist – scientific – scientifically.

2. Translate the adjectives paying attention to the negative prefixes:

incorrect, unkind, dissimilar, immovable, irresistible, disloyal, uncomfortable, incomparable, illogical.

3. Give verbs of the same root and translate them:

assistance, education, establishment, expression, existence, receiver, equipment, exhibition, reference.

4. Translate the following word-combinations:

a few words, the language of science, to connect with, to change an object from a state of rest to a state of motion, to act over a distance, in this case, to take into account, to lift a weight, to throw a stone, the scientific sense of the word, to result in, the amount of, the applied force, in order to, to multiply by, to be equal to, to divide by, kinds of energy.

5. Translate the sentences paying attention to different meanings of the words in bold type:

1. Many electric stations use the power of water.

2. One horse power equals 75 kilogram – meters.

3. This power station was built 10 years ago.

4. Scientists achieved good results in constructing semiconductor devices.

5. The application of this device results in better operation of the equipment.

6. These forces change the direction of motion.

7. The change of the state of matter was caused by heat.