Technical text for listening. Технические тексты для аудирования

80 The load is (3) attached to one end of the rope, and the other end is pulled to move the load. The more pulleys that are used in a system, the less (4) effort is required to move a load. 2.6. Wheel and Axle A Wheel and Axle form a simple machine. The wheel is (1) fixed to the axle (central shaft) and together they (2) transmit and increase force. A small turning force is (3) applied to the wheel, producing an increased force on the axle. In this way, (4) heavy loads can be moved with less effort. This (5) principle is used in steering wheels. 2.7. What is Motion? Everything in the world is in motion. Some forms of motion we can see clearly, such as the (1) flight of an airplane. But even objects that seem (2) still, such as rocks and buildings, contain atoms (tiny particles) that move minutely, or (3) vibrate. The Earth itself is moving around the sun, and the entire (4) universe is expanding. All motion (5) requires force to start, to change speed or direction, or to stop. 2.8. What is Force? The push or pull that starts an object (1) moving is a force. Forces not only make things move, they can also (2) speed up or slow down a moving object, make it change (3) direction, or even distort its (4) shape. Generally, the (5) stronger the force, the greater the (6) effect it has on an object. 2.9. Dynamics The study of dynamics is part of a wide (1) field of study called mechanics, which (2) investigates physical forces. Dynamics is concerned with the (3) nature of the forces that (4) cause objects to move. There are many different kinds of such forces, for example, (5) gravity and friction, which produce many different kinds of motion. The type of motion produced will depend on the size, direction, and rate of the forces that cause it to happen. 2.10. What is energy? (1) Everything happens because of energy: without it, there would be no life on Earth. Scientists (2) classify energy into several different types, (3) including chemical energy, light energy, and (4) nuclear energy. Most types of energy can switch from one form to another. It is when energy switches form that things happen, or work is done. In a car, for example, (5) gasoline provides chemical energy, which turns into mechanical energy, heat energy, electrical energy, and sound energy when the (6) engine is started. 2.11. Types of Energy Scientists (1) divide energy into seven main types. These include heat energy, which (2) raises the temperature of matter, electrical energy, which (3) converts into other energy forms, including heat and light, and chemical energy, contained in (4) fuels. All energy that comes directly or indirectly from the sun is known as (5) radiant energy and makes up the electromagnetic spectrum. 2.12. Change of state Many substances can (1) exist in more than one state - as a solid, liquid, or gas. Which state they are in (2) depends on their temperature and pressure. At (3) certain temperatures, under normal atmospheric pressure, some substances change state. Liquids, for example, may (4) become solids or gases, and gases may (5) condense into liquids. Elements change state, under normal pressure, at specific temperatures, known as (6) melting (or freezing) and boiling (or condensation) points.