Science notes, unit 10

Machines

Textbook Science Year 5 (DLP), pages 217–230

What this chapter covers

You can explain that machines are tools that help us do work more easily and faster (10.1.1)
You can state the function of a tool and name the simple machines in it (10.1.1)
You can describe how simple machines are combined in a tool so that it works well (10.1.2)
You can explain why the combination of simple machines in a tool is important (10.1.3)
You can list the characteristics of a sustainable tool and say why such tools matter (10.1.4)
You can suggest and sketch an improved tool that has sustainable characteristics (10.1.5)

A school bag is heavy, a jar lid is tight and a bunch of paper will not stay together by itself. Humans solve problems like these with tools. In this unit you will find out how tools work, how simple machines are combined inside them, and what makes a tool sustainable.

10.1Machines and life

Machines are tools or equipment that help us do our work more easily and faster.

Aina and Danish want to join paper sheets to make a scrapbook. Danish says, "Use a stapler." The staple is a wedge: it makes holes and joins the paper sheets. The stapler also works on the lever principle.

A purple stapler being pressed to join paper sheets — A stapler joins paper. The staple is a wedge and the stapler is a lever.

Other tools for a scrapbook: scissors cut paper, a hole punch makes holes, a pencil sharpener sharpens pencils and adhesive tape sticks paper together.

Revision: the simple machines

These are the simple machines you will find in the tools in this unit.

Simple machine	What it does	Example
Lever	Turns about a fulcrum so that a force can move a load	Nail clipper, stapler
Wedge	Cuts, splits or pushes things apart	Staple, saw, knife
Screw	Fastens parts together	Screw in a wristwatch, bottle cap
Wheel and axle	Makes turning easier	Hand crank, doorknob, watch crown
Pulley	Pulls a rope to lift or move a load	Pruning saw, crane
Gear	Turns and moves other parts	Wristwatch

Did you know? A lever has three parts: the force (where you push or press), the load (what is moved) and the fulcrum (the point it turns on).

Name two tools that you can use to make a scrapbook and state what each tool does.

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Any two: scissors (cut paper), stapler (join paper), hole punch (make holes), pencil sharpener (sharpen pencils), adhesive tape (stick paper).

10.2Combination of functions in simple machines

Most tools have more than one simple machine. Each machine does its own job, and the jobs work together.

Tool	Simple machine	Its function in the tool
Mechanical pencil sharpener	Wheel and axle	The hand crank is easier to turn, so the wedge can work
Mechanical pencil sharpener	Wedge	Sharpens the pencil
Nail clipper	Lever	The force is at the thumb, the load is at the nail and the fulcrum is between them
Nail clipper	Wedge	The cutter cuts the nail
Wristwatch	Gear	Moves and turns the hands
	Screw	Fastens the parts
	Wheel and axle	The crown sets the watch
Pruning saw	Wedge	The blade cuts branches
	Screw	Fastens the parts of the saw
	Pulley	Pulls the wedge

A mechanical pencil sharpener with a hand crank and a pencil being sharpened — The crank (wheel and axle) turns the wedge that sharpens the pencil.

A nail clipper with the force, fulcrum and load labelled — Nail clipper: force at the thumb, fulcrum in the middle, load at the nail.

Inside of a wristwatch showing gear, screw and crown — A wristwatch combines a gear, a screw and a wheel and axle.

A pruning saw with its wedge blade, screw and pulley rope labelled — A pruning saw combines a wedge, a screw and a pulley.

A nail clipper is not "just a wedge". The body is a lever and the cutter is a wedge. Look for every simple machine in the tool.

More examples from the textbook answers: pruning shears (secateurs) have a lever, a screw and a wedge; a doorknob has a lever and a wheel and axle; a hand drill has a wedge, a screw and a wheel and axle. The wedge of the drill makes holes, and the wheel and axle make its handle easier to turn.

Which simple machines are in a mechanical pencil sharpener?

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Wheel and axle (the hand crank) and wedge (the part that sharpens the pencil).

10.3Why the combination is important

Look at two situations.

A cyclist sitting by a bicycle whose pedals have come off — Situation 1: the pedals are no longer joined to the bicycle.

A girl looking at a pair of scissors that she can no longer use — Situation 2: the scissors cannot be used any more because a part is missing.

When a part is missing, the simple machines can no longer work together. A bicycle cannot be pedalled and scissors cannot cut. The combination of simple machines is important so that the tool functions well.

Think: a screw only works because it has spiral thread grooves. Without them it cannot grip and fasten the parts.

Why must the screw in a pair of scissors stay in place?

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The screw holds the two blades together so the lever and wedge work together. Without it the scissors cannot function well.

10.4Sustainable tools

Ana's mother uses a special cutter and a grater to prepare food. These are sustainable tools: they simplify work, save time, are safer to use than a knife and are easy to clean. The washing machine and the vacuum cleaner are sustainable too. Ana's waste bin is heavy to push, so it is not.

Wheel diagram of six characteristics of sustainable tools — Six characteristics of a sustainable tool.

Characteristic	What it means
Suitability of the materials	Made from materials that suit the job
Longer life span	Can be used for a long time
Easy to maintain	Easy to clean and repair
Low cost and save money	Not expensive to make or use
Environmentally friendly	Does not harm the environment
Safe to use	Does not hurt the user

Sustainable tools make our work easier and faster and save time, cost and energy. In industry they increase the quantity and quality of products, which can be managed more efficiently, faster and more safely at low cost.

A blue waste bin with a lid — Ana's waste bin: how could it be improved?

Improving the waste bin

Add wheels so it is easier to push (easier work, saves energy). Divide the inner space for recyclables and compost (environmentally friendly). Keep using the bin if it still works well (longer life span, saves money).

Think: a rope on a simple pulley can break if the load is heavier than the rope can take. A bigger rope, or more pulleys so that a smaller force is needed, solves the problem.

Take care with sharp and hot tools when you make things such as the adhesive tape container in the Fun Science activity.

Name three characteristics of a sustainable tool.

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Any three: suitable materials, longer life span, easy to maintain, low cost and save money, environmentally friendly, safe to use.

Pictures: Science Year 5 (DLP) textbook, pp. 217–230 (stapler p. 218, sharpener and nail clipper p. 220, wristwatch and pruning saw p. 221, situations p. 222, bin and wheel diagram p. 225, tools and pulley p. 230).

Summary

Idea	Remember
Machine	A tool that makes work easier and faster
Combination of simple machines	Several simple machines with different functions make a tool work well
Missing part	The tool cannot function well
Sustainable tool	Suitable materials, longer life, easy to maintain, low cost, environmentally friendly, safe
Why sustainable tools matter	Easier, faster work; saves time, cost and energy