Why does a heavy ship float?
A hollow hull pushes aside a lot of water. The water pushes upward with a force called buoyancy.
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Everyday Life & Technology
Everyday puzzles and fascinating ideas to explore.
Building & moving
How does pedalling move a bicycle forward?
Pedalling turns the front chainring. The chain carries the movement to drive the rear wheel.
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What helps a paper bridge stay strong?
Folding changes a sheet's shape. A suitable folded shape bends less easily under the same load than a flat sheet.
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How does a zipper work?
The slider guides two rows of matching teeth together so they interlock. Moving the other way separates them.
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How does a seesaw work?
A seesaw turns around its support. Each side's turning effect depends on weight and distance.
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Why do wheels make moving a load easier?
A box slides its bottom across the ground. Wheels roll instead.
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How do gears work together?
When two external gears mesh, each pushes the other in the opposite direction. A small wheel must turn more times than a large one to pass the same number of teeth.
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How does a crane keep its balance?
A load on a long crane arm pulls the crane to one side. A counterweight and a stable base help balance it.
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Why does a screw stay in wood?
A ridge winds around a screw: its thread. Turning makes the thread grip the wood.
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How does a pulley system work?
In a pulley system, several sections of rope can support a load. This can reduce the pulling force needed.
Open learning page →Water, materials & warmth
How does water reach the tap?
Drinking water is collected, checked and treated when needed. Pipes carry it under pressure to homes.
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How does a refrigerator keep food cool?
A refrigerator moves heat from inside to outside. A special fluid in closed pipes takes in heat inside and releases it outside.
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Why does soap help us wash our hands?
Soap helps loosen dirt, grease and many germs from hands. Rubbing spreads it over the skin; water rinses loosened material away.
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Why does a towel soak up water?
Tiny spaces lie between a towel's fibres. Water clings to suitable fibres and spreads through these spaces.
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Why does a window mist up?
Warm moist air can cool against cold glass. Invisible water vapour then becomes tiny liquid drops.
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Why does wet laundry dry?
Water leaves wet laundry and enters the air as invisible water vapour. This is evaporation.
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What changes when ice melts?
Ice takes in heat from its surroundings and becomes liquid. This is melting.
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How does a vacuum flask keep a drink warm?
An insulated flask slows heat exchange with its surroundings. Its walls and lid reduce that exchange.
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Why does sugar dissolve in water but sand does not?
Sugar spreads through water in particles too small to see individually. It has dissolved.
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Why does air expand when warmed?
In warmer air, tiny particles move faster on average. If the air can expand freely, it takes up more space.
Open learning page →Light, sound & forces
Why does my shadow move with me?
Your body blocks light. Less light reaches the ground behind it: that is your shadow.
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What can a magnet attract?
An ordinary magnet attracts certain materials, such as iron and many steels. It does not attract wood or paper, but not every metal either.
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How does a battery make a lamp light up?
A battery can supply electrical energy. In the simple lamp model, a closed path must run from one battery terminal through the suitable lamp to the other terminal.
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Why does a magnifying glass make things look bigger?
A magnifier's curved lens changes the direction of light. An object held suitably close appears larger.
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How does music come from a speaker?
An electrical signal moves a thin surface back and forth inside a speaker. This diaphragm makes air vibrate.
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How does an echo happen?
An echo is reflected sound. Your call travels to a surface and back.
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Why does a reflector shine in a lamp beam?
A reflector sends light roughly back towards where it came from. That makes it look bright in a lamp's beam.
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How does friction help us brake?
During braking, suitable surfaces rub together. Some motion energy becomes heat, and the vehicle slows down.
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How does a mirror redirect light?
A mirror reflects light in an orderly way. You see an object in it when light from the object reaches your eye through reflection.
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Why do soap bubbles show colours?
A bubble's thin film reflects light at its outer and inner surfaces. The returning light waves overlap.
Open learning page →Detectives & Puzzles
Observe carefully, check clues and explain answers: discover puzzles and the limits of guesses.
Explore topics →Machines & Vehicles
How do vehicles move, and how do machines help? Discover forces and parts through clear examples.
Explore topics →Media & Invention
Create original games, pictures, stories and inventions. Plan small steps, test ideas and respect permission, privacy and other people’s rights.
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