Pulleys and the wheel and axle — Engineering for kids
A fixed pulley stays in one place and only changes the direction of your pull — you pull down to lift the load up, with the same force. A movable pulley rides up with the load; two rope sections share the load, so you need half the effort but pull twice as much rope. With ideal pulleys, effort = load ÷ number of rope sections holding the load. A wheel and axle (a well winch, a doorknob, a steering wheel) has MA = wheel radius ÷ axle radius.
Wheel and axle: MA = wheel radius ÷ axle radius; effort = load ÷ MA.
Use it for: Science lessons on pulleys, a flagpole or well at school, and building a model crane.
Worked example: 🪝 A load of 600 N hangs from a pulley system in which 3 rope sections hold up the load. What effort is needed, in newtons? (ideal pulleys) → 200
The 3 rope sections share the load equally.
600 N ÷ 3 = 200 N.
Check: 3 × 200 N = 600 N, but you pull 3 m of rope to lift it 1 m ✓
Work it out in your head or on paper, then tap your answer — or type it and press Check. Stuck? Press “Show me how”.
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🏁 Lesson 14 test
20 questions. Check each answer, then go to the next one. Get 16 or more right to pass.
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