Bicycles, toys, buses, cycle rickshaws and autorickshaws are complex machines, but all of them contain simple machines such as the wheel and axle and pulley. Simple machines make work easier and let us do things beyond our capacity: a cart with wheels and axle moves heavy loads with less force, and pulleys lift heavy objects. Even a big bus is made of many interconnected small machines.
Simple machines are ancient. Huge stone temples in India were built by quarrying, transporting, carving and assembling stone, using chisels and hammers, and lifting blocks with inclined planes, levers and pulleys.
In Activity 1, students list things around them, such as a knife or a vegetable peeler, and find whether each is a simple machine or made of them.
| For | Materials | Tools |
|---|---|---|
| Toys from trash | Cardboard, plastic pipe, bottles, spoons, straws, bottle caps, paper, ice cream sticks, thread, rubber bands, glue, tape, glue gun, clothes clips, all pins, balloon, colours, chopsticks | Scissors, metre scale, cutter |
| Bicycle work (at least 5 to 6 bicycles) | Oil or grease | Spanner set, wrenches, chain brush, tyre levers, air pump |
A lever is a fixed bar or handle that moves around a fixed point called the hinge or fulcrum. Examples: a spoon opening a tin lid (tip under the lid, force at the other end) and a seesaw. Toys: catapult (single lever), lazy tongs and robotic arm (many levers).
For each toy, draw a sketch with accurate measurements and write instructions for a first-time user.
A propeller is a wheel with blades that push through water or air. The elastic band boat is made by pasting ice cream sticks into a boat shape, making paddle wheels from slit bottle caps and sticks, passing a straw through them, tying a rubber band from the boat's tip to the straw, winding it and placing the boat in water.
A wheel and axle is wheels held together by a rod so they move together, like car wheels. Two sets of wheel and axle make:
| Rubber band car | Air balloon car | |
|---|---|---|
| Body | Clothes clips joined by a straw | Old plastic bottle with chopsticks taped on |
| Wheels | Bottle caps with holes in their exact centres on toothpicks or skewers | Bottle caps fixed on chopsticks with glue |
| Power | Rubber band wound at the back | Air from a balloon fixed to a straw |
| To run | Wind and release on stable ground | Blow the balloon, then release the finger from the straw |
A windmill generates energy from wind. Its working model combines a propeller and a wheel and axle, using cardboard, chart paper blades, straws, glue and a cutter. Students can also ask ChatGPT, an AI chatbot, for ideas on making fun things from waste.
A bicycle uses wheels, wheels and axles, levers and pulleys. Its moving parts work together to transform the rider's effort into motion.
| Part | Function |
|---|---|
| Brake pads | Grab the wheels to resist motion |
| Brakes | Slow or stop the bicycle (rim, disc, drum) |
| Chain | Transfers power to the rear wheel |
| Chain rings, sprocket | Guide the chain; transmit power from pedal to chain |
| Frame | Main structure; supports rider and joins parts |
| Handlebars | Hold and steer |
| Hubs | Centre of wheel; let it spin around the axle |
| Kickstand | Keeps bicycle upright |
| Cycle light | Visibility and safety |
| Pedals | Where the feet apply force |
| Rims | Support tyres; braking surface for rim brakes |
| Saddle | Where the rider sits |
| Seatpost | Joins saddle to frame; adjustable |
| Spokes | Join rim to hub; strength and stability |
| Tyres | Traction and cushioning |
| Problem | Solution |
|---|---|
| Rusting of parts | Clean with sandpaper; apply oil or paint |
| Loose parts | Tighten with the right tools |
| Wheels not moving freely | Oil the moving parts |
| Flat tyres | Check air pressure regularly |
Students check the brake, chain, spokes, kickstand, handlebars and tyre (Table 3.3), and visit a bicycle repair shop or invite a mechanic. Useful questions: what to check before riding, how to adjust saddle height, how to clean a bicycle, how to know tyres need air, how a puncture is repaired, how often to oil the chain, how to fix squeaking brakes and how wheels are aligned.
Further ideas: build a chain reaction machine from simple machines made of trash; estimate how many times a wheel turns in 10 metres using the rim's circumference; think about how cycling helps health and the environment. Related jobs: bicycle mechanic, toy maker and engineer.