16. Underline the correct tense form in each of the following sentences.

1. People have always polluted / had always polluted their surroundings.

2. Before we came, they had discussed / were discussing the problems that threaten human life on Earth.

3. With the development of industrial cities, which put huge amounts of pollutants into small areas, the problem has become / had become urgent.

4. Our forests are disappearing / had disappeared because they are cut down or burnt.

5. She was relieved to hear that he had saved / saved those animals.

6. If nothing is done / had done about it, one day nothing will be able to live in the seas.

7. He said that he has developed / had developed new methods.

17. Put the verbs in brackets into Past Perfect or Past Simple.

1. We ….. (to have) a lot of trouble because we ….. (to lose) our passports.

2. She really….. (to like) him because he ….. (to help) her.

3. We ….. (to get) into the restaurant only because we ….. (to reserve) our places.

4. Chris ….. (to own) that car for 5 years before he ….. (to sell) it.

5. I ….. (to be) in Greece for 7 months before I ….. (to move) to Spain.

6. They ….. (to study) English before they ….. (to move) to Canada.

7. They ….. (to ride) their bikes before they ….. (to meet) their friends.

18. Put the verbs in brackets into the correct tense.

A: What 1) ….. (you / to do) when I 2) ….. (to call) at eight, Burt?

B: I 3) ….. (to work) in the garden because the wind 4) ….. (to blow down) the fence during the night.

A: Oh, 5) ….. (you / to manage) to fix it?

B: Yes, I ….. (to do ) it eventually, but it 7) ….. (to be) very hard work. I 8) ….. (to ask) my neighbor to help in the end. Why 9) ….. (you / to call) me?

A: I 10) ….. (to want) to tell you about the factory. It 11) ….. (to close down) yesterday.

B: I know. The company 12) ….. (to have) problems for a long time before they finally 13) ….. (to decide) to close down the factory.

A: I 14) ….. (to hope) they would change their minds about it, though. It 15) ….. (to be) a part of the town for years.

B: Well, at least everyone who worked there 16) ….. (now / to find) a new job. That’s good news.

Unit 7 facts about forces

LEAD-IN

1. What is force? Give examples of forces acting on people and objects around us.

2. What kinds of forces do you know? How are they related to motion?

READING

1. Read the text and give the definitions of:

• force;

• motion;

• Newton’s three laws of motion;

• net force

Facts about Forces

Force is a word that has lots of different meanings and different uses. For instance, there is electrical force, the force of gravity, and the force of magnetism. Nuclear force holds atoms together. Another kind of force is mechanical force. The word force means a push or a pull, or to be a little bit more scientific, it means anything that causes the shape or motion of an object to change. The amount of force is measured in units called newtons, named after the scientist Sir Isaac Newton (definition of a Newton: the force required to accelerate a one kilogram object by one meter per second squared).

Force and Motion. Force and motion describe everyday things that are happening all the time. Hundreds of times every day, you use force and motion. Did you just pick up a pencil? – Force and motion. Did you turn a page? – Force and motion. Force and motion are also parts of a complicated branch of science, called physics.Motionmeans moving something from one place to another. In fact, the word motion is a form of the word move.

Newton's Three Laws of Motion. Sir Isaac Newton is well known for his three laws of motion as well as for other scientific breakthroughs. Here are Sir Isaac Newton's three laws of motion.

Law 1 - An object moving in a straight line will continue moving in a straight line, unless acted on by an outside force. Also, an object at rest will stay at rest. The word for this is inertia.

Law 2 - Force will cause a change in the motion of an object. The change in motion depends on the amount of force and the mass of the object. There is a formula for this F=ma (force equals mass times acceleration).

Law 3 - For each action, there is an equal and opposite reaction.

Force is a vector, which means that it has both direction and magnitude. When several forces act on an object, the forces can be combined to give a net force.

If multiple forces combine to give a net force that is zero, then the object will not accelerate; the object will either remain motionless or continue moving at a constant velocity. For example, if a person pushes a shopping cart with a force equal in magnitude to the force of friction that opposes the cart's motion, the forces will cancel, giving a net force of zero. As a result, the cart will move down the aisle with a constant velocity. If the person suddenly stops pushing the cart, the only force acting on the cart is the frictional force. The velocity of the cart drops to zero.

LANGUAGE DEVELOPMENT

4. Group the following words into three columns: nouns, adjectives and verbs. Some of them fit into more than one column.

Force, different, meaning, use, electrical, gravity, magnetism, nuclear, atom, mechanical, push, pull, scientific, mean, shape, motion, object, change, scientist, describe, day, pencil, page, place, law, straight, line, continue, stay, rest, inertia, action, equal, opposite, reaction, direction, magnitude, combine, give, remain, constant, velocity, person, friction, oppose, cancel, result, cart, breakthrough, acceleration, mass, definition, part, frictional, drop.

NOUNS	ADJECTIVES	VERBS

5. Match each word from the text with its synonym:

1. force a) form

2. motion b) weight

3. shape c) application

4. definition d) discovery

5. use e) power

6. breakthrough f) determination

7. mass g) movement

6. Match the first part of the sentence (1-7) with the second one (A-G).

1. An object moving in a straight line will continue moving in …..

2. Force and motion are also parts of a complicated …..

3. When several forces act on an object, the forces can …..

4. Sir Isaac Newton is well known for his three laws of .….

5. The amount of force is measured in units called …..

6. The change in motion depends on the amount …..

7. The word force means a push or a pull, it means …..

1. ….. motion as well as for other scientific breakthroughs.

2. ….. branch of science, called physics.

3. ….. newtons, named after the scientist Sir Isaac Newton.

4. ….. of force and the mass of the object.

5. ….. a straight line, unless acted on by an outside force.

6. ….. anything that causes the shape or motion of an object to change.

7. ….. be combined to give a net force.

7. Match the English phrases with their Ukrainian equivalents:

1. nuclear force a) галузь науки

2. constant velocity b) закон руху

3. scientific breakthrough c) ядерна сила

4. straight line d) наукове відкриття

5. branch of science e) постійна швидкість

6. law of motion f) протилежна дія

7. opposite reaction g) пряма лінія

8. Read the clues and complete the crossword:

	1		2
3
							4										5
					6						7
			8
							9
10

Across: 3 A person who works in a science. 7 The force which tries to stop one surface sliding over another. 8 The force which keeps a thing in the position or state it is in until it is moved or stopped by another force. 9 A thing that can be seen or felt. 10 The natural force by which objects are attracted to each other.

Down: 1 Something done; the way in which something moves or works. 2 A force exercised by a body in reply to another force, which is of equal strength and acts in the opposite direction. 4 The act, way, or process of moving. 5 The act of moving or condition of being moved. 6 The heaviness of something, as measured by a certain system. 7 Measurement of a power that changes or may produce change of movement in a body on which it acts or presses.

LISTENING

9. Pre-listening: match the English words and phrases with their Ukrainian equivalents:

1. turning moment	ричаг
2. pivot	обертатися
3. force	гаєчний ключ
4. fulcrum	вісь обертання
5. leverage	cила
6. revolve	точка обертання
7. spanner	точка опори