4º NS Unit 6 – MACHINES AND ENERGY (Student´s Book and Activity Book SOLUTIONS)

HOMEWORK:

1. Check the solutions to the exercises you did last week from the books of N.S. (Student´s Book and Activity Book).

UNIT 6 Natural Science – MACHINES AND ENERGY

4º NS STUDENT´S BOOK (solutions)

PAGE 83

SOLUTIONS

1 Simple machines – screw, saw, garden shears, retractable tape measure, scraper, saw.

2 Screws are used for holding materials together.

3 Simple machines work in opposition to natural forces; They are often powered by human physical energy.

4 Electricity from various sources such as wind, the Sun, coal, gas, petroleum, water, etc.

5 Pupils’ own answers.

6 Pupils’ own answers.

7 Screw, wedge, gas, helmets, goggles.

PAGE 84

SOLUTIONS

1 a.false; b.true; c.false; d.true; e.true.

PAGES 86, 87

SOLUTIONS

1 A table; a screw; It holds the table legs in place.

2 Pupils’ own answers.

3 – 1 lever, stapler – class; 2 lever, scissors – class; 3 lever, door handle – class; 4 lever, human arm – class.

4 Galileo’s experiment with an inclined plane demonstrated that as an object travels down the plane due to the force of gravity, it travels progressively faster. He developed the theory that simple machines do not create energy, they transform it. He identified five classical simple machines.

PAGES 88, 89

SOLUTIONS

1 Pupils’ own answers.

2 Pupils’ own answers.

3 Radiator – thermal machine; calculator – information processing machine; motorbike – mechanical machine; computer – information processing machine; freezer – thermal machine.

4 Skateboard – human physical energy; car – oil, gas, or electricity; surfboard – water energy; sailing boat – wind energy.

5 A power saw; special gloves and goggles; to protect her skin or eyes against small pieces of wood.

4º NS ACTIVITY BOOK (solutions)

PAGE 32

SOLUTIONS

1 – SIMPLE machines: inclined plane, wedge, pulley, screw, wheel and axle, lever.

COMPLEX machines: mechanical machines, thermal machines, information processing machines.

2 – Answers. 2. Effort – 3. Simple – 4. People – 5. Energy – 6. Load – 7. Pulley.

PAGE 33

SOLUTIONS

3 – a. screw – b. wheel and axle – c. wedge – d. inclined plane – e. pulley – f. lever.

4 – Answers: You can use an inclined plane to move objects from one level to another. – The round shape of the wheel reduces the amount of friction. – The axle is in the centre of a wheel. – You can use a wedge to cut or to hold objects in place. – A wedge is made up of two inclined planes together. – You can use a screw to tighten or join objects together.

5 – Archimedes.

PAGE 34

SOLUTIONS

6 – Answers :

CLASS 1 LEVER: a. effort – b. fulcrum – c. load – Examples: A seesaw and a crowbar.

CLASS 2 LEVER: a. fulcrum – b. load – c. effort – Examples: A wheelbarrow and a nutcracker.

CLASS 3 LEVER: a. fulcrum – b. effort – c. load – Examples: A hockey stick and a stapler.

7 – a. mechanical machine – b. information processing machine – c. thermal machine.

PAGE 35

SOLUTIONS

8 – a. oil (WRONG) people (CORRECT) – b. harder (WRONG) easier (CORRECT) – c. thermal (WRONG) mechanical (CORRECT) – d. mechanical (WRONG) thermal (CORRECT) – e. heaters (WRONG) computers (CORRECT) – f. force (WRONG) motion (CORRECT)

9 – a. gas or oil – b. the Sun – c. people – d. wind

10 – Student´s own answers. Examples: a. Do not run with them in your hands. – b. Do not use it near water.