Physics
Physics projects for class 6 to 8: 141 ideas.
Each project below opens to its own page with what it shows, the science behind it, the materials, safety, step-by-step instructions, what you should see and viva questions. Many can be made from things at home; where a kit helps, the page links one.
Other subjects for class 6 to 8: Chemistry, Biology, Maths, Earth and space, Electronics and robotics, Environment, Computing and coding.
Balloon-powered car
Air rushing backwards out of the balloon pushes the car forwards. This is Newton’s third law: every action has an equal and opposite reaction.
Simple electric circuit with a switch
Electricity flows only round a complete loop. The switch opens and closes the loop, turning the bulb off and on.
Sink or float, and the clay boat
Whether something floats depends on its density and its shape. A ball of clay sinks, but the same clay shaped into a boat floats, because it pushes aside more water.
Air pressure holds up water
Air pushes on everything around us. When the glass is turned over, the air pressure pushing up on the card is enough to hold the water in.
CD hovercraft
Air from the balloon forms a thin cushion under the CD. The cushion cuts friction with the table, so the hovercraft glides.
Hydraulic arm with syringes
Pressure applied to a liquid in a closed system is passed on equally in every direction (Pascal’s law), so pushing one syringe moves its partner and lifts the arm.
Electromagnet
An electric current in a coil of wire makes a magnetic field. Wound round an iron nail, the coil becomes a magnet you can switch off, and more turns of wire make it stronger.
Simple electric motor
A coil carrying current in a magnetic field feels a force and turns. Scraping the insulation off only half of one end switches the current on and off at the right moments, so the coil keeps spinning.
Periscope
Light reflects from a plane mirror at the same angle at which it arrives. Two mirrors at 45 degrees send the light down the tube, so you can see over a wall.
Wind turbine that lights an LED
A small DC motor works as a generator when its shaft is turned: the spinning blades turn motion energy into electrical energy that lights the LED.
Static electricity and a jar electroscope
Rubbing a balloon moves electric charge onto it. A charged object attracts light things, and in the electroscope the two foil leaves get the same charge and push apart.
Pinhole camera
Light travels in straight lines, so rays from the top of an object pass through the pinhole and land at the bottom of the screen. The image is upside down.
Rubber band powered car
Winding the rubber band stores elastic potential energy, which turns into motion (kinetic) energy as it unwinds and turns the axle.
Plastic bottle vacuum cleaner
A small fan blows air out of the back of the bottle, lowering the pressure inside, so outside air rushes in through the nozzle carrying dust and paper bits with it.
Bottle-cap water wheel that lifts a weight
Falling water pushes on the cups of the wheel and makes it turn. The turning axle winds up a thread and lifts a small weight, so the energy of moving water becomes useful work.
Thread spool crane with a fixed pulley
A single fixed pulley does not make a load lighter, but it changes the direction of the pull, so you lift a load up by pulling down. That is why cranes, flagpoles and wells use pulleys.
Ruler seesaw: balancing coins at different distances
A lever balances when the weight times its distance from the pivot is equal on both sides. One coin far from the middle balances two coins placed half as far away.
Does a steeper ramp need more force? Cardboard ramp test
An inclined plane lets you move a load up with less force than lifting it straight, but over a longer distance. The gentler the slope, the smaller the pull needed and the longer the path.
How a stick’s shadow changes through the day
The shadow of a fixed stick is long in the morning, shortest around midday and long again in the evening, and it swings from west to east as the Sun moves across the sky. Shadow length depends on how high the Sun is.
Tissue box rubber band guitar: what changes the pitch?
Sound is made by vibration. A thin, tight or short rubber band vibrates faster and gives a higher note; a thick, loose or long one vibrates slower and gives a lower note. The hollow box makes the sound louder.
Water bottle xylophone: pitch and the amount of water
Tapping a glass bottle makes the glass and the water vibrate, and more water makes the vibration slower and the note lower. Blowing across the top vibrates the air instead, so the bottle with the most water gives the highest note.
Why does a clay ball sink but a clay boat float?
The same lump of clay sinks as a ball but floats as a bowl, because the bowl shape pushes aside much more water. Floating depends on the shape and the water displaced, not only on the weight.
How much salt makes an egg float?
An egg sinks in plain water but floats in salty water. Dissolving salt makes the water denser, so it pushes up harder on the egg. Measuring the salt needed turns a trick into a real experiment.
Balloon in a bottle: air takes up space
A balloon hung inside a sealed bottle will not blow up, because the air already in the bottle has nowhere to go. Make a small hole in the bottle and the balloon inflates easily, proving that air is real and takes up space.
The bottle that crushes itself: air pressure and cooling
A capped bottle of warm air shrinks and crumples when it is cooled quickly, because the cooled air inside takes up less space and presses less, while the air outside keeps pressing in. It shows that air pressure is a real and strong push.
Simple pendulum: does length or weight change the swing time?
The time for one swing of a pendulum depends on its length, not on how heavy the bob is or how wide it swings (for small swings). A longer pendulum swings more slowly. Pendulum clocks are built on this rule.
Which shoe sole grips best? Friction on a tilting ramp
Friction is the force that stops things sliding. A rough rubber sole needs the board to be tilted much more steeply before it slides than a smooth plastic sole, so the angle at which an object starts to slide is a simple measure of friction.
Two-spool block and tackle that halves the effort
A movable pulley hanging with the load shares the weight between two lengths of string, so you need only about half the force to lift it, but you must pull twice as much string. Adding pulleys trades distance for force.
Floating needle compass that finds north
Stroking a steel needle with a magnet turns it into a weak magnet. Floated on water so it can turn freely, the needle lines up north to south, because the Earth itself acts like a giant magnet.
Mapping a bar magnet’s field with a small compass
A small compass placed near a bar magnet points along the field at that spot. Joining many such points draws the field lines, which loop from the north pole round to the south pole and crowd together where the field is strongest.
Paper spiral snake that spins over warm air
Warm air is lighter than cool air and rises. A paper spiral hung above a warm surface spins as the rising air pushes on its sloping coils, showing convection, the way heat spreads in air and water.
Black tin versus white tin: which gets hotter in the sun?
A dark surface soaks up most of the sunlight that falls on it and gets hot, while a white or shiny surface reflects most of it and stays cooler. This is why we wear light colours in summer and why solar heaters are painted black.
Which cup keeps tea hot the longest? Insulation test
Heat flows from hot things to cooler surroundings. Materials like thermocol, cloth and air pockets slow this flow and are called insulators, while metal lets heat through quickly. A lid matters because much heat escapes with rising warm air and steam.
Bottle and straw thermometer that shows expansion
Liquids expand when heated and shrink when cooled. Coloured water in a sealed bottle rises up a narrow straw when the bottle is warmed and falls when it is cooled, which is exactly how a liquid thermometer works.
Bottle with three holes: water pressure grows with depth
Water squirts furthest from the lowest hole in a bottle, because the weight of all the water above it presses on it. Pressure in a liquid increases with depth, which is why dam walls are thickest at the bottom.
Ketchup sachet diver that sinks when you squeeze
A sachet with a small air bubble just floats in a bottle of water. Squeezing the bottle raises the pressure, squashes the bubble, and the sachet becomes denser and sinks; let go and it rises. Submarines and fish control their depth the same way.
Ice cream stick catapult: how far does a pom-pom fly?
Pulling the arm down stores energy in the bent stick and rubber bands, and letting go turns it into the motion of the pom-pom. More bend means more stored energy and a longer flight, and the launch angle changes the distance too.
Marbles in a ruler groove: passing on a push
When one marble rolls into a line of touching marbles, one marble shoots off the far end; roll two in and two leave. The push, or momentum, passes right through the line, as in a Newton’s cradle.
Paper helicopter: wing length and fall time
A strip of paper with two folded wings spins as it falls, because air pushing on the slanted wings makes it turn. Longer wings catch more air and slow the fall, while adding paper clips makes it fall faster. Air resistance is a real force.
Plastic bag parachutes: does a bigger canopy fall slower?
A parachute slows a fall because its wide canopy pushes against a lot of air. Bigger canopies take longer to fall with the same load, and a small hole in the top makes the fall steadier instead of swinging.
Balloon rocket on a string: action and reaction
Air rushing out of the balloon’s neck pushes the balloon the other way along the string. The bigger the balloon, the further it travels. This is Newton’s third law, the same rule that lifts a real rocket.
Cardboard marble roller coaster: height, speed and loops
A marble released from high up gains speed as it rolls down, trading height (potential energy) for speed (kinetic energy). It can climb a hill or go round a loop only if it started higher than the top of that hill or loop, and friction steals a little energy all the way.
Cardboard bird that balances on a fingertip by its beak
A cardboard bird with coins hidden in its wing tips balances on its beak and even wobbles back upright when pushed. Adding weight far forward and low moves the bird’s centre of gravity to just below the beak, so it cannot topple.
Cardboard castle drawbridge raised by thread and spools
A drawbridge is a lever hinged at one end, raised by threads that run over pulleys at the top of the gate and are wound on an axle. The model shows how a lever, pulleys and a wheel and axle work together to lift a load with a gentle turn of a handle.
Village well model: a wheel and axle that lifts a bucket
Turning a large wheel moves a small axle with greater force, so a bucket of water can be lifted with a light push on the handle. The bigger the handle circle compared with the axle, the easier the lift but the more turns needed.
A screw is a wrapped ramp: paper triangle on a pencil
Wrapping a paper triangle round a pencil turns its sloping edge into a spiral thread, just like a screw. A screw is an inclined plane wound round a rod, which is why it goes in with little force but needs many turns.
Wedge test: which blade shape splits clay most easily?
A wedge turns a push on its wide back into strong sideways pushes at its thin edge, which split material apart. Thin, long wedges split clay with less force than short, blunt ones, which is why knives and axes are sharpened.
Three classes of lever on one working board
Levers differ by where the fulcrum, load and effort sit. A seesaw has the fulcrum in the middle, a wheelbarrow has the load in the middle, and tongs have the effort in the middle. Three working ice cream stick levers on one board show each class and how much they help.
Steel spoon mirrors: why one side flips your face
The back of a shiny spoon is a convex mirror and always shows a small, upright, wide view. The bowl side is a concave mirror: it shows your face upside down from far away and large and upright when very close.
Kaleidoscope from old CD case strips and a chips tube
Three mirrors set in a triangle reflect light again and again, turning a few coloured beads into a symmetrical pattern of many images. It shows how reflection works and how multiple reflections multiply images.
Making a rainbow with a mirror in a bowl of water
Sunlight looks white but is a mixture of colours. Water with a mirror in it acts like a prism, bending each colour by a slightly different amount, so the reflected beam fans out into red, orange, yellow, green, blue, indigo and violet on the wall.
The bending pencil: refraction in water, oil and glass
A pencil standing in a glass of water looks broken at the surface because light bends when it passes from water into air. Different liquids bend light by different amounts, and a coin hidden under the rim of a cup reappears when water is poured in.
Water drop magnifier: a lens from a single drop
A drop of water on clear plastic has a curved top, like a convex lens, and makes small print look bigger. A rounder, smaller drop magnifies more. It shows how lenses in magnifying glasses, spectacles and microscopes work.
Spinning colour disc: seven colours blend into white
A disc painted with the seven rainbow colours looks almost white when spun fast, because the eye cannot keep up and mixes the colours together. White light is a mix of all colours, which is the reverse of a prism splitting it.
Twanging ruler: how length changes pitch and loudness
A ruler held over the edge of a table and twanged vibrates and makes a sound. A short overhang vibrates fast and gives a high note; a long overhang vibrates slowly and gives a low note. A harder twang makes a louder sound but not a different note.
Cardboard ear trumpet that collects faint sounds
A wide cone gathers sound waves from a large area and funnels them into the ear, so faint sounds become louder and clearer. Used the other way round, it sends your voice in one direction like a megaphone.
Which spinning top lasts longest? Paper plate and bottle-cap tops
A top stays upright while it spins fast, then wobbles and falls as friction slows it. Tops with a wide, heavy rim and a sharp point usually spin for longer.
Egg drop cushion: how much padding keeps a boiled egg whole?
A soft cushion makes the egg stop more slowly, so the force on it is smaller. The same change in motion over a longer time means a smaller force.
Rubbed balloon lifts paper bits and bends a thin stream of water
Rubbing a balloon on hair gives it an electric charge. A charged object attracts light things like paper bits and even bends a stream of water.
Finding the centre of gravity of odd cardboard shapes with a plumb line
Every object has one point where its weight seems to act, the centre of gravity. A shape hung from a pin comes to rest with this point directly below the pin, which lets you find it with a plumb line.
Which spoon gets hot first? Steel, wood and plastic with butter and beads
Heat travels along a solid by conduction. Metals pass heat quickly, while wood and plastic pass it slowly, so a bead stuck on a metal spoon with butter drops off first.
Convection currents: coloured hot water rising and cold water sinking
Warm water is lighter than cold water, so it rises, while cold water sinks. This movement forms convection currents which carry heat through liquids and air.
Archimedes’ principle with a rubber band balance and an overflow can
An object in water feels lighter. The upward force, the buoyant force, equals the weight of the water it pushes aside, and the rubber band shows it by shrinking.
Blow over a paper strip and watch it rise: fast air, low pressure
When you blow across the top of a paper strip it lifts instead of staying down. Fast-moving air has lower pressure than still air, so the stronger pressure below pushes the paper up.
Coin drops into a glass when the card is flicked: inertia tricks
Objects keep their state of rest unless a force acts on them. When the card is flicked quickly, the coin does not move sideways and drops straight down into the glass.
Rolling beats sliding: pencils as rollers under a heavy book
It is much easier to roll a load on rollers than to slide it over the surface. A rubber band stretches less when the load rolls, showing that rolling friction is smaller than sliding friction.
Speed of sound from an echo off a wall, a clap and a stopwatch
Sound travels at a finite speed, about 340 metres every second in air. A clap that returns as an echo from a far wall lets you work out this speed with only a stopwatch and a tape.
Why the sky is blue and sunsets are red: milk in water and a torch
Tiny particles scatter blue light more than red light. Light through a slightly milky tank looks blue from the side and orange-red from the far end, like a sky and a sunset.
Which ball bounces highest? Drop height and floor surface test
A ball stores energy when it is squashed and gives most of it back as it bounces. Different balls and surfaces return different fractions of the energy, so the bounce height changes.
Cardboard gear train: how gears change speed and direction
Gears pass motion from one shaft to the next. A small gear driving a large one turns it more slowly but with more turning force, and neighbouring gears turn in opposite directions.
Pepper runs from soap: surface tension and a soap-powered boat
The surface of water behaves like a thin stretched skin. Soap weakens this skin where it touches, so the stronger pull from the surrounding water drags the floating pepper outwards.
Rolled newspaper tube bridge: how much can it carry?
A flat sheet of paper bends easily, but the same paper rolled into a tube becomes strong. The bridge shows how shape, not material, decides strength.
Arch bridge versus beam bridge from cardboard strips
An arch pushes sideways on its supports and carries a load by compression. A flat beam of the same material sags because the bottom is stretched.
CD and balloon hovercraft that glides on a cushion of air
A thin layer of air under the disc removes most friction, so the hovercraft slides a long way with a tiny push. It shows how reducing friction changes motion.
CD and paper Newton colour disc that turns white when spun
White light is a mixture of the seven spectrum colours. When a disc painted in rainbow sectors spins fast, the eye blends the colours and sees a pale white or grey.
Tin-can telephone: does a tight string carry sound better?
Sound travels along a taut string as vibrations. A loose string cannot carry the vibration well, so the voice becomes faint.
Drinking straw pan pipes: tube length and pitch
A shorter air column vibrates faster and gives a higher pitch. Seven straws of different lengths make a simple scale.
Cardboard model houses with different roofs: which stays cooler?
A roof of insulating material like thermocol slows the passage of heat into the house, so the inside stays cooler. The test compares four roof types.
Rubber-band powered cardboard car on CD wheels
A twisted rubber band stores elastic energy that turns the axle and moves the car. Winding it more stores more energy and the car goes farther.
Paddle-wheel boat from a bottle and a rubber band
The wheel pushes water backwards and the water pushes the boat forward, as in Newton’s third law. The twisted rubber band supplies the energy.
Archimedes screw water lifter from a bottle and a plastic tube
Turning a spiral of tube lifts water uphill without a pump. The device is a screw that lifts water in a few turns, used for thousands of years.
Pot-in-pot clay cooler: how evaporation keeps food cool
Water evaporating from wet sand between two clay pots takes heat from the inner pot. The test shows a temperature drop with no electricity.
Pinhole camera from a chips tube that shows an upside-down world
Light travels in straight lines, so light from the top of an object goes to the bottom of the screen through a tiny hole. The image on the screen is upside down.
Milk carton periscope that lets you see round corners
Two mirrors set at 45 degrees reflect light twice and bring the view from a higher point to your eye. It shows the laws of reflection.
Ice-cream stick tilt maze: guiding a marble by gravity
A marble always rolls downhill. Tilting the board changes its direction and speed, so the player has to plan the slopes.
Rubber-band spring balance with a cardboard scale and straw pointer
The stretch of a rubber band grows with the load. A scale marked with known weights turns it into a simple balance that measures weight.
Pizza box solar oven that warms a cup of water
Foil reflects sunlight into the box, a clear cover traps heat, and a black cup absorbs it. The test shows how reflection, absorption and trapping of heat make a solar cooker.
Balloon-skin tin can drum where sound makes rice dance
Sound is a vibration. When a loud sound hits the stretched balloon, it vibrates and makes grains of rice jump, so we can see the vibration.
Popcorn: does soaking the kernels change how many pop?
Each popcorn kernel holds a tiny drop of water. When heated, the water turns to steam and builds pressure until the hard shell bursts. You test dry, lightly soaked and over-soaked kernels and count the percentage that pop.
Cooking time against size: potato cubes in boiling water
Heat moves into a potato from the outside by conduction, so a bigger piece takes much longer to cook through. By boiling cubes of different sides and noting when a fork goes in, you find the link between size and cooking time.
What dries clothes fastest: sun, shade, wind or folding?
Water leaves wet cloth by evaporation, which speeds up with heat, wind and open surface area. You hang identical wet cloths in different conditions and weigh them each hour to find which dries fastest.
Shadow size against torch distance: similar triangles at home
Light travels in straight lines, so the shadow of an object grows larger as the torch moves closer. Measuring several distances and comparing ratios shows that the shadow follows similar triangles.
How tall must a mirror be to see your whole body?
To see your whole body in a flat mirror, the mirror need be only half as tall as you, and it does not depend on how far you stand. You test this with a small mirror, a tape and a friend.
Glass bottle xylophone: water level and pitch
The pitch of a note from a tapped bottle depends on the amount of water in it: more water gives a higher note when tapped. You tune bottles into a scale and learn how vibration speed sets pitch.
Ruler twang: how overhang length changes pitch
A ruler pressed on a table and plucked gives a higher note when less of it hangs over the edge. By counting vibrations per second for each overhang length, you find how length controls frequency.
How many sheets of paper can a fridge magnet still hold?
The pull of a magnet gets weaker as the gap between it and the steel grows. By stacking sheets between a magnet and a steel surface, you measure how quickly magnetic force falls with distance.
Coat hanger balance: weigh sugar, salt and rice by comparison
A balance compares two masses by checking that they pull equally on both sides of a pivot. You build one from a hanger and use it with a reference weight to measure the mass of kitchen items.
Water siphon from a kitchen tube: height difference and flow rate
A siphon moves water up and over a barrier without a pump, because the longer falling column of water pulls the liquid along. You measure how the height difference between two buckets changes the flow rate.
The stuck jar lid: why warm water loosens a metal cap
Metals expand when heated, and a thin metal lid heats faster than the glass jar below it. A tight cap that will not turn becomes loose after a short dip in warm water, which shows thermal expansion at work.
Which surface colour heats up fastest in the sun? Four can test
Dark and dull surfaces absorb more sunlight than light and shiny ones. The temperature rise of equal cans of water under the same sun shows which colour is best for a solar heater and which suits a roof.
Vertical Savonius turbine from two halves of a plastic bottle
A vertical-axis wind turbine spins whichever way the wind blows. The curved half-bottle blades catch more push on the open side than the round side, so the rotor keeps turning.
Overshot against undershot water wheel lifting the same load
Water can turn a wheel by weight from above (overshot) or by push from below (undershot). Timing how fast each wheel lifts a small weight shows which uses water more efficiently.
Hand-crank generator: voltage against cranking speed
Turning a small DC motor by hand makes a voltage, so the motor acts as a generator. Faster cranking gives higher voltage and brighter light, showing that mechanical energy changes into electrical energy.
Pot-in-pot clay cooler that keeps vegetables fresh without electricity
Water evaporating from wet sand between two clay pots cools the inner pot. This is how farmers can store vegetables cooler without a fridge.
Sprinkler irrigation model from a drilled pipe and a bucket head
A rotating or fixed sprinkler spreads water as small jets over a field. The model shows how water pressure, hole size and height decide how far and how evenly water falls.
Canal lock model that lifts a boat between two water levels
A lock raises or lowers boats by letting water in or out of a chamber between gates. The model shows how water finds its own level and moves a boat with no engine lift.
Archimedes screw water lifter from a bottle and a coil of tube
A screw turning in a tilted tube lifts water upward, an idea used for thousands of years to irrigate fields. The model shows how a simple machine moves water uphill without a motor.
Hand pump model from a bottle, tube and two one-way flaps
A hand pump uses a piston and one-way valves to lift water from a well. The model shows how pushing and pulling the handle makes water move in one direction.
Straw rocket launcher: which fin shape flies the farthest?
A paper rocket is pushed off by a puff of air, and its fins keep it pointing straight. Changing only the fin shape while keeping everything else the same is a fair test of how fins help flight.
Gaganyaan-style crew capsule with a parachute to land an egg astronaut
A crew capsule coming back from space is slowed by a parachute and lands softly. A larger parachute canopy gives more air drag and a slower fall, which protects the passenger.
Bounce height of cricket, tennis and rubber balls on grass, concrete and sand
How high a ball bounces depends on both the ball and the surface. Some of the ball’s energy is lost as sound, heat and a dent in the surface at each bounce, which explains why pitches matter in cricket.
Flat sole, studs and spikes: friction on a muddy tray
Friction is the force that stops a shoe from slipping. On wet mud, the grip depends on the sole pattern, because studs and spikes dig in and rubber flat soles slide on a film of water.
Ruler-drop reaction time: dominant hand, other hand and a warning sound
The distance a ruler falls before you catch it tells how fast you react. Comparing hands and signals shows what can speed up or slow down a response, which is important in cricket and sprint starts.
Paper planes: dart, glider and wide-wing flight distance and time
A paper plane flies by gliding: its wings make lift and the nose is pushed forward by the throw, while drag slows it. Different shapes trade speed for glide time.
Kite flying physics: tail length, string angle and wind speed
A kite stays up because the wind pushes on it at an angle. The forces of wind, weight and string tension balance. A longer tail steadies the kite, and a higher wind speed raises the string angle.
Balance point of a cricket bat, a hockey stick and a bicycle pump
Every object has a balance point, the centre of gravity, where its weight seems to act. In sports equipment it is not at the middle, and where it lies changes how the object feels in the hand.
Standing long jump: does an arm swing add distance?
The distance of a jump depends on the take-off speed and angle. Swinging the arms adds to the speed of the body’s launch, which is why athletes use them.
30 metre sprint speeds of a class timed with a pair of stopwatches
Average speed equals distance divided by time. Timing a short run shows differences in speed in a class, and also how reaction time of the timekeeper can add error.
Playground seesaw: where must two children sit to balance?
A seesaw balances when the turning effect (moment) on one side equals that on the other. A lighter child must sit farther from the pivot to balance a heavier child.
Carrom striker slide: how powder changes friction and stopping distance
Carrom players sprinkle fine powder on the board to make the striker glide. Measuring how far a striker slides with and without powder shows how a thin layer lowers friction.
Which fruits and vegetables float? Predict and test
Some fruits and vegetables float and some sink in water, depending on how much of the body is air and how heavy it is for its size. Predicting before testing is how scientists work.
Foil boat: how many coins can it carry before it sinks?
The shape of a boat decides how much it can carry. A wide boat with high sides pushes aside more water and so carries more than a flat sheet.
Magnet pole push: two toy cars that chase and run away
Every magnet has two poles. Unlike poles pull together and like poles push apart, and we can use the push to move a small car without touching it.
Torch and coloured cellophane: mixing lights on a wall
Coloured light mixes differently from paint. Where beams of red, green and blue light overlap, we see new colours, and all three together look almost white.
Toy shadow length: does a higher torch make a shorter shadow?
The length of a shadow depends on where the light is. A high light gives a short shadow and a low light gives a long one, like the Sun at noon and in the evening.
Toy car ramp: does a steeper slope make the car go farther?
A car rolling down a slope speeds up. A steeper ramp gives it more speed, so it rolls farther along the floor.
Cardboard gears with paper teeth that turn each other
Two gears with teeth that mesh turn in opposite directions, and a small gear spins faster than a big one.
Drinking straw whistle: shorter straw, higher sound
Sound is made by vibrations. A shorter vibrating column of air gives a higher sound, and a longer one gives a lower sound.
Does sound travel through water? The spoon and bowl test
Sound can travel through liquids and solids as well as air. In water it travels even faster than in air.
Feel your voice: humming throat and dancing salt on cling film
Voice is a vibration. We can feel it in the throat and see the vibration make salt grains jump on a stretched sheet.
Ice cube melting: sun, shade, cloth and steel plate
Heat melts ice. The speed of melting depends on how warm the place is and whether the ice is covered or not.
Does water take up more room when it freezes?
Water expands a little when it freezes. Ice takes up more space than the same water, which is why ice floats.
Simple diamond paper kite and a flying test
A kite flies because wind pushes on it at a slant and string holds it. The tail keeps it steady.
Paper plane race: which fold flies the farthest?
Wing shape and fold change how far a plane flies. A fair test means launching each plane the same way and measuring the distance.
Paper clip on the nose: does weight help a plane glide?
The position of weight changes how a plane flies. A little weight in the front makes it steady, but too much makes it dive.
Static comb: lifting paper bits and bending a water stream
Rubbing some things together gives them an electric charge, called static electricity. A charged comb can pull tiny paper bits and bend a thin water stream.
Rain stick from a cardboard tube: the sound of falling rain
Many grains falling past obstacles make a sound like rain. We hear the vibrations of grains hitting the tube walls and the pins.
Long spring waves: transverse and longitudinal pulses you can see
A long coiled spring or a stretched coil of telephone cord can carry two kinds of waves: sideways shakes make transverse waves and push-pull shakes make longitudinal waves. In both, the wave travels along but the coils only move back and forth.
Which rubbing makes the strongest charge? Balloon and paper bits test
Rubbing a balloon with different materials gives different amounts of static charge, and a charged balloon picks up small paper bits. Counting the bits lifted ranks the materials from weak to strong charging.
Butter on spoon handles: which material conducts heat fastest?
Spoons of steel, aluminium, wood and plastic with butter dabbed on the handles are placed in hot water, and the butter melts and drops first on the best conductor. It shows that metals conduct heat well and wood and plastic poorly.
Convection currents drawn with food colour in hot and cold water
Hot water is lighter than cold water, so a drop of colour in hot water rises in a plume while colour in cold water sinks. This movement of a fluid carrying heat is convection and drives sea breezes and boiling in a pot.