The scientific meaning of the words "work", "energy" and "power".

As previously mentioned, many words that we use in our everyday speech assume a more precise and often restricted meaning in the language of science. The words "work", "energy" and "power" considered in this article are quite familiar to everyone; nevertheless, their use in scientific terminology presents certain difficulties. Discuss­ing these three terms in some detail is the subject of our present article for we know of their being often misused.

The word "work" may serve as an example. Besides its being an English word in common usage, it is also a scien­tific term which has a special meaning when used in me­chanics.

When we are standing and holding a heavy weight, when we are studying or teaching at the institute – we say than we are working. Studying may he very hard. We know that it will make you tired at times; nevertheless, no physicist will ever call it work. The scientific term "work" is much more restricted. Mechanical work is per­formed only when a force moves some object through a distance.

One can perform work by lifting a box from the floor. Pushing the box along the floor against friction also means doing work. According to physical laws you cannot per­form any work scientifically speaking by pushing an auto­mobile which is standing on the road, unless it starts mov­ing. Thus, in order to do mechanical work two conditions are necessary, namely, there must be a force and it must act through a distance. Generally speaking, the greater the force and the distance moved, the greater the work performed.

Work and energy are very closely related. Indeed, one may say that the energy of a body or system is the capa­city of that system or body for doing work. Power is re­lated to both work and energy. It is the rate of performing the work in a unit of time.

While energy is the capacity for work, power is the quantity of work done in a unit of time. When a kilogram is lifted to a height of one metre, we say that a kilogram-metre of work is accomplished. The amount of the accomp­lished work does not depend on the time spent on lifting this weight.

Considering power requires considering the rate of per­forming the work. For example, if a weight is lifted to a height of one metre in one second, twice as much power will he required than in case that very weight were lifted to a height of one metre in two seconds.

If someone carried a 15-kg box up the stairs in 10 sec, the staircase being 6 m high, he would work at the ave­rage rate of 90 kgm divided by 10 sec, or 9 kgm per se­cond.

Measuring power we generally use such units as waits, kilowatts, and kilogram-metres per second. Seventy five kg.m.s. (kilogram-metres per second) or 736 W (watts) form a horse-power. A horse power is a unit for measuring the amount of work performed per second.

Discussing the term "energy", we shall follow the transformation of one form of energy into another.

Exercise 2. Read and translate the following words and phrases:

term, amount, object, science, average, friction, move, condition, accomplish, precise, measure, relate, restrict, perform, power, capacity, weight, as previously mentioned, quite familiar, no physicist will ever call it .., scientific term, according to.., namely, one may say, twice as much, in order to… .

Exercise 3. Give English equivalents of the words:

кінська сила, термін, одиниця, енергія, ват, потужність, кількість, робота, піднімати, предмет, умова, кіловат, секунда, приклад, рух, тіло, відстань, обмежувати.

Exercise 4. Answer the questions.

1. What is the subject of the present article?

2. What terms are discussed in this article?

3. Is the term “pressure” dealt with here?

4. When is mechanical work performed?

5. Do you perform any work while lifting a box from the floor?

6. When is mechanical work performed?

7. What conditions are necessary in order to do mechanical work?

10. What is necessary for considering power?

11. What units are used for measuring power?

Exercise 5. State if the following sentences are true to the fact or false. Correct the false sentences.

1. When you are studying you can say that you are working.

2. To do mechanical work there must be a force.

3. The greater the force and the distance moved, the greater the work that has been performed.

4. Power is related to both work and energy.

5. For measuring work we use such units as watts and kilowatts.

6. The “work” is a scientific term which is never used in our everyday life.

Exercise 6. Write out the keywords and phrases and make up a plan.

Exercise 7. Retell the text.