WHAT IS ENERGY?

Date: 2015-10-07; view: 394.

Wherever you are sitting as you read this, changes are taking place: light bulbs are heating the air around them, the wind might be rustling leaves, or sunlight might be glaring off.

Every change that occurs—large or small—involves energy. Imagine a baseball flying through the air. It hits a window, causing the glass to break.The window changed from a solid sheet of glass to a number of broken pieces. The moving baseball caused this change—a moving baseball has energy. Even when you comb your hair or walk from one class to another, energy is involved.

In science energyis defined as the ability to do work. Work is done when a force causes something to move. One also can define energy as the ability to cause change. When work is done, something moves and a change occurs. When work is done and a change occurs, energy moves from place to place or changes from one form to another.

Turn on an electric light, and a dark room becomes bright. Turn on your CD player, and sound comes through your headphones. In both situations, energy moves from one place to another. These changes are different from each other.This is because energy has several different forms—electrical, chemical, radiant, and thermal. Each of you can name and show some examples of everyday situations which involve forms of energy. Is the chemical energy stored in food the same as the energy that comes from the Sun or the energy stored in gasoline? Radiant energy from the Sun travels a vast distance through space to Earth, warming the planet and providing energy that enables green plants to grow. When you make toast in the morning, you are using electrical energy. In short, energy plays a role in every activity that you do.

If we push a book across the desk so that it accelerates, we give the book an impulse – we apply a force on the book for a period of time. However, the book also moves some distance during this time. That is, we also apply the force across a distance. Whenever we apply a force on an object across a distance, we say that we are doing work on that object. Work is the transfer of energy to an object by applying a force to the object through some distance. When we do work on the object, we change some condition of the object, either its position in space or its velocity. If we change its position, such as lifting a mass above the surface of the earth, the work we do is stored as gravitational potential energy. If we change its velocity, the work is stored as kinetic energy.

12. Translate the following words and word combinations into English using your active vocabulary:

включать (электрический свет); объект; сила; звук; перенос (передача) энергии; применять силу; происходить, случаться; тепловая энергия; химическая энергия; обогревать (нагревать) планету; ослепительно сверкать, ярко светить; условие; скорость; положение в пространстве; наушники; бензин; импульс; энергия излучения солнца; накапливать энергию; поверхность Земли.