Vocabulary tasks:

8. Answer the following questions to the text.

1. Where is Newton's analysis of motion summarized?

Newton's analysis of motion is summarized in his famous "three laws of motion"

2. What does the Newton’s first law state?

The first Newton’s law stat was: Every body continues in its state of rest or of uniform speed in a straight line unless acted on by a nonzero net force.

3. What can we call inertia?

The tendency of a body to maintain its state of rest or of uniform motion in a straight line is called inertia.

4. Does Newton's first law hold in every reference frame?

No, Newton's first law does not hold in every reference frame.

5. What is noninertial reference frame?

The noninertial reference frames is reference frames where the law of inertia does not hold, such as the accelerating reference frame discussed above.

9. Are the following statements about the text true or false?

1. Newton's first law of motion is far from to Galileo's conclusions. - False

2. Newton's first law is often called the law of relativity. - True

3. Reference frames in which Newton's first law does hold are called velocity reference frames. - True

4. The accelerating reference frame are called inertial reference frame. - False

5. Every body continues in its state of rest or of uniform speed in a straight line unless acted on by a nonzero net force. - True

10. Match the first part of the sentence (1 –6) with the second part (a-f).

1. C) Newton's analysis of motion is summarized in his famous "three laws of motion".

2. F) The Principia is a great work

3. A) Newton's first law does not hold in every reference frame.

4. E) We can assume that reference frames fixed on Earth's rotation.

5. D) How can we be sure a reference frame is inertial or not?

6. B) The law of inertia is valid in reference frames.

a  in every reference frame.

b in reference frames.

c  in his famous "three laws of motion".

d is inertial or not?

e  on Earth's rotation.

f a great work.

11. Complete the sentences with words from the box.

acceleration - motion -  law - velocity - concepts - inertia

1. They introduced partially defined concepts .

2. Newton's first law is often called the law of inertia.

3. The more mass a body has, the harder it is to change its state of inertia .

4. We can say that mass is a measure of the motion of a body.

5. Newton perceived that the acceleration will change.

6. The velocity depends on the mass of the object as well.

Unit three text the law of conservation of mass and energy

All bodies possess mass, which is an inherent property of all matter. In our experiences we have observed that the outward appearance of matter is constantly changing, so that it would reasonable to assume that its mass is also undergoing some sort of change. To test this assumption let us take a lump of coal and burn it. The mass of this lump is certainly much greater than the ashes that result from its burning, but should we collect the gases formed and account for all the other materials concerned in the burning and weight them, we should find that the total mass has remained unchanged. All the experience accumulated in the study of every change in matter shows that in all the changes the total mass is neither increased nor diminished.

But every change in matter involves a change in energy. This energy makes its appearance in a number of forms such as heat, energy, electrical energy, chemical energy, radiant energy, kinetic energy (energy possessed by moving bodies), or potential energy.

Experiments carried out over a long period of time have shown that energy is like mass in that energy in all transformations is neither created nor destroyed. This generalization is known as the law of conservation of energy. The distribution of this energy between bodies, however, is altered without a great deal of difficulty. For example, if a piece of hot metal is placed into cold water, the metal is cooled and the water is heated so that the metal loses energy and the water gains it. We also find that energy can be freely transformed from one variety to another. Thus the heat energy derived from the burning of coal may be changed into the kinetic energy of the locomotive. Similarly, the kinetic energy possessed by falling water can be transformed into electricity. If we were to make a close study of such transformations, we should find that a definite quantity of energy of one kind always gives a definite equivalent quantity of another.

In any action involving the change of one form of energy into another no gain or loss in total energy takes place. In other words: whenever a quantity of one kind of energy is produced, an exactly equivalent amount of another kind must be used up.

Both the principle of conservation of mass and the principle of preservation of energy afford a simple, direct approach in setting up a material balance and an energy balance. In both cases a relatively complete accounting can be made from the knowledge of what goes into the system and what comes out, what is the efficiency of a given system, whether it is a blast furnace or a locomotive.