Simple Machines
Primary 6 · Science and Elementary Technology
Simple Machines
Lesson 5 of 5
13 min
Let's begin
At a building site, Habimana piled bricks high in a wheelbarrow and ran with it down a steep path. Halfway down, the wheelbarrow tipped over. The bricks landed on his foot.
Simple machines make work easier. Used carelessly, they also make accidents easier. In this lesson you will learn the dangers and how to prevent them.
| Machine | Danger | How to prevent it |
|---|---|---|
| Wheelbarrow | Tips over, rolls away downhill, crushes feet. | Load the heavy part over the wheel, spread the load evenly, never pile it too high, go slowly on slopes and wear closed shoes. |
| Pulley and rope | The rope breaks and the load falls on someone; fingers are caught in the wheel. | Check the rope for wear, never stand under a raised load, keep fingers away from the groove and wear gloves. |
| Levers (crowbar, seesaw) | The bar slips; fingers are pinched; a child falls off the seesaw. | Place the crowbar firmly. On the seesaw, sit facing each other, hold the handles and never jump off while your partner is up in the air. |
| Wedges (axe, knife, panga) | Deep cuts; chips of wood fly out. | Cut away from your body, keep people well back when splitting wood, keep blades sharp and store them in a cover. |
| Screws and nails | Sharp points in feet and fingers. | Use the right screwdriver, and pick up any screws or nails that fall on the floor. |
| Scissors | Cuts and stab wounds. | Walk, never run. Carry them closed, points down, and pass them handles first. |
| Ramps and jacks | A load rolls back down; a vehicle falls. | Never stand below a load on a ramp. Block the wheels. Never go under a vehicle held only by a jack. |
Warning
The danger zone is under a raised load, below a load on a slope and in front of a swinging blade. Keep yourself, and everyone else, out of it.
A machine in good condition is a safer machine.
Machines are only as safe as the people using them. Use a machine only for its own job, think about the people around you, and speak up when you see someone in danger.
Tip
Before you use any machine: Check it, Load it right, Keep out of the danger zone.
Try each one first, then tap Show answer to check.
Where should the heaviest bricks go in a wheelbarrow, and why?
Answer: Towards the front, over the wheel. The wheel then carries most of the weight, so the barrow is easier to lift and less likely to tip.
A bucket of cement is being lifted by a pulley. Where must you never stand?
Answer: Directly under the load, in case the rope breaks.
Ishimwe splits firewood while his little sister holds the log steady for him. What is wrong?
Answer: Her hands are in the danger zone of the axe. Nobody should hold the log; it should stand on a chopping block, and everyone should stand well back.
What you learned today
Sources and credits
Quick check
How should you carry a pair of scissors?
