Simple Machines in Daily Life

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1Summary 重點摘要

Levers, wheels and axles, pulleys and ramps are simple machines that save effort — they are everywhere.

2Vocabulary cards Vocabulary

3Step by step Steps

1. Step 1: Meet the leverA lever is a simple machine that turns around a fixed point called the fulcrum. The centre post of a seesaw is the fulcrum: the heavier child sits near it and the lighter child sits farther out, and the two can still balance. Understanding levers helps us see that even a person with little strength can lift something heavy with the help of a tool. A common mistake is thinking the heavier child must sit far out to balance; it is just the opposite — the heavier side must sit nearer the fulcrum for the two ends to level.
2. Step 2: The saving clothes pegA little clothes peg also hides the secret of the effort-saving lever. When you clip socks with a peg, the parts your fingers squeeze work like two little bars — the longer the squeeze point, the easier it is to press the jaws open. Many other little tools in daily life use levers: scissors cut paper with a lever, a bottle opener lifts the cap with a lever, and a nail clipper hides one as well. They are all good helpers that save our effort, waiting for you to discover them. A common mistake is thinking effort-saving tools must be complicated; many handy tools are simply simple levers.
3. Step 3: Turning wheel and axleA wheel and axle is made of a big wheel and a small axle: turn the big wheel and the axle turns with it. Twist the round knob of a door handle, the axle inside turns too, and the lock opens easily; a tap's handle is a wheel and axle too — twist it and the water flows. The wheel and axle make turning easy and smooth — a good helper hidden all around us. A common mistake is failing to spot wheel-and-axles; look carefully at door handles, taps and screwdrivers, and you will find them everywhere.
4. Step 4: Pulleys change directionA pulley is a small wheel with a groove that can turn around its centre. When the flag is raised, a pulley is fitted at the top of the pole: we pull the rope downwards, and the flag rises slowly along the pole. A pulley's skill is changing the direction of the pull, so we can stand still on the ground and still send things up high; the pulley on a clothesline works the same way. A common mistake is thinking a pulley makes us stronger; its skill is changing direction, making the pull handy and saving both effort and trouble.
5. Step 5: Ramps save effortA ramp is a sloping surface and one of the most effort-saving simple machines in the world. Put a heavy schoolbag on a slanted board and push it slowly up onto a platform — much easier than lifting it straight up. Workers build ramps from wooden planks to push goods onto lorries, and wheelchair users go up and down on barrier-free ramps, all using the effort-saving secret of the ramp. A common mistake is thinking a ramp only makes the path longer; the path is a little longer, but pushing becomes far easier — that is exactly the value of the ramp.
6. Step 6: Hunt for machinesNow that you know simple machines, be a little detective at home. Find three common tools and look closely at which simple machine each one uses: scissors cut paper with a lever, a door handle turns the lock with a wheel and axle, the clothesline pulley sends clothes up high, and the slope at the back of a lorry is an inclined plane. Tell your family what you find with confidence, and you are a little machine expert. A common mistake is thinking simple machines are hard to find; they are everywhere at home and in the classroom, waiting for careful eyes.

4Diagrams Diagrams

5Worked example Example

6Common mistakes Mistakes

7Quick check Quick check

8Recap Recap

• Simple machines save our effort.
• Levers work on a pivot; the seesaw is an example.
• Wheels and axles turn with less effort, like door handles.
• Pulleys change force direction — that is how flags rise.
• Ramps make heavy loads easier to move, like access slopes.