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Physics

The rules behind everyday life

Why does light bend? Why do we lean forward when a vehicle brakes? Discover the rules behind everyday events.

  • 16labs
  • 83experiments
  • 2articles
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Forces and motion

From a toy train to a satellite: how things move, and how forces change that.

5 labs21 experiments

Curved Motion and Energy Lab

Throw it, spin it, loop it: curved motion and the conservation of mechanical energy.

  1. 01Projectile launcherDoes a faster throw stay in the air longer?
  2. 02Centripetal force turntableDouble the spin rate: does it need double the force?
  3. 03Satellite orbitsDo higher satellites move faster?
  4. 04Incline and winchA ramp saves force. Does it save work too?
  5. 05Roller coasterStart as high as the loop top: will it make it round?

Simple Machines Lab

Levers, pulleys and ramps all save force, at the price of a longer path.

  1. 01LeverKeep the same point but pull in another direction. Does the force change?
  2. 02PulleysHow much force does a pulley save, and how much farther does your hand travel?
  3. 03RampA longer ramp needs less force. Does it also need less work?
  4. 04WindlassA longer crank needs less force. What is the price?
  5. 05Pulley blockDoes the same pulley block always have the same efficiency?

Mass, pressure and buoyancy

Weigh it, press it, lower it into water: how dense matter is, and how a liquid holds up a ship.

2 labs10 experiments

Pressure and Buoyancy Lab

Pressure in a liquid grows with depth; buoyancy is the difference between the push from below and the push from above.

  1. 01Pressure gaugeDeeper water means more pressure. What about the container’s shape, or how much water it holds?
  2. 02Ship lockHow does a boat climb from the low river to the high one?
  3. 03Weighing methodDoes an object feel more buoyancy the deeper it goes?
  4. 04Overflow canHow large is the buoyant force, exactly?
  5. 05SubmarineHow does a submarine dive and surface?
  6. 06ShipSteel is denser than water. Why does a steel ship float?

Heat

Where heat comes from and where it goes; how a cylinder of gas turns heat into work.

2 labs11 experiments

Heat and Changes of State Lab

Watch the temperature curve: where the heat goes during melting and boiling.

  1. 01Test tube in a water bathIt is still being heated, so why does the temperature stop rising?
  2. 02Beaker on a hot plateDoes water always boil at 100 °C?
  3. 03Heating iceDoes all the heat go into raising the temperature?
  4. 04Two beakers side by sideDoes a bigger temperature rise mean more heat was absorbed?
  5. 05Rods and matchsticksDo all metals conduct heat equally well? Does glass conduct at all?
  6. 06Black, white and silver cansDoes a black object that absorbs more heat also lose less?

Thermodynamics Lab

One cylinder with a piston covers the gas laws, the first law and the Carnot cycle.

  1. 01Molecular speedsWhen it gets hotter, does every molecule speed up?
  2. 02Squeezing with the handwheelHow must you squeeze for pV to stay fixed?
  3. 03Heating in a water bathIs pressure proportional to the Celsius temperature?
  4. 04Energy ledgerDoes squeezing a gas always warm it? Does taking in heat always warm it?
  5. 05Carnot cycleCould a frictionless engine reach 100 % efficiency?

Sound and waves

A vibration that travels is a wave; the part you can hear is sound.

2 labs11 experiments

Sound Lab

What carries sound, and what sets its pitch, loudness and timbre.

  1. 01Bell in a bell jarWith the air pumped out, is the bell still ringing?
  2. 02Three sound pathsIn which material does sound travel fastest?
  3. 03Ruler on a desk edgeIf you can see it vibrate, can you always hear it?
  4. 04Drum and sound meterTwice as far away: is the sound half as loud?
  5. 05Sources and oscilloscopeSame note, so how can you tell the instruments apart?
  6. 06Ultrasonic rangingHow can an echo measure a distance?

Vibrations and Waves Lab

Start with a mass on a spring; see a vibration become a wave, and waves add up to a standing wave.

  1. 01Spring oscillatorPull it further: does it swing more slowly?
  2. 02Simple pendulumDoes a heavier bob swing faster?
  3. 03Driven oscillatorDrive it faster: does it shake harder?
  4. 04Wave demonstratorWhen a wave passes, do the particles travel with it?
  5. 05Standing wave on a stringWill any frequency make a steady standing wave?

Electricity and magnetism

Close a circuit, then see the invisible fields around the wires.

3 labs17 experiments

Electricity bench (middle school)

Close the circuit and read the meters: from series and parallel through Ohm’s law to the electromagnet.

  1. 01Two bulbsDoes a bulb use up some of the current that flows through it?
  2. 02Rheostat circuitIf the voltage doubles, does the resistance double too?
  3. 03Resistance wiresDouble the diameter of a wire: does its resistance only halve?
  4. 04Kerosene flasksDoes a bigger resistance let less current through and so heat up less?
  5. 05FuseIs a circuit safer if the fuse is replaced by copper wire?
  6. 06ElectromagnetDoes only the current decide how strong an electromagnet is?

Electricity bench (high school)

Cells have internal resistance, capacitors charge and discharge, coils resist a change in current: read the meters, watch the oscilloscope.

  1. 01Cell and rheostatIs the voltage across a battery its EMF?
  2. 02Small bulbDoes a small bulb have a fixed resistance?
  3. 03CapacitorDoes a capacitor fill up the instant it is connected?
  4. 04Coil and bulbWhen the switch opens, does the bulb always flash?
  5. 05LC circuitDoes a capacitor discharging through a coil empty in one go?
  6. 06Transformer kitCan a transformer step up direct current?

Electric and Magnetic Fields Lab

Electric and magnetic fields are invisible; measure them with a probe, an electron beam and a coil.

  1. 01Charged spheres and probeWhere the field is zero, is the potential zero too?
  2. 02Parallel-plate capacitorPull the plates apart. Must the field between them get weaker?
  3. 03e/m apparatusDoes the magnetic force speed the electron up?
  4. 04Magnet and coilWith the magnet resting inside the coil, is the current largest?
  5. 05AC generatorWhen the flux is largest, is the EMF largest too?

Light and atoms

How light bends, forms images and interferes; why energy inside atoms comes in lumps.

2 labs13 experiments

Modern Physics Lab

The photoelectric effect, alpha scattering, the hydrogen spectrum: energy in light and atoms comes in lumps.

  1. 01Zinc plate and electroscopeThe photoelectric effect
  2. 02PhotocellCurrent, voltage and stopping voltage
  3. 03Mercury lamp and filtersMeasuring Planck’s constant
  4. 04Gold foil and microscopeAlpha-particle scattering
  5. 05Hydrogen tube and spectrometerThe hydrogen spectrum
  6. 06Franck–Hertz tubeEnergy levels and excitation

SHORT READS

Start from everyday questions

01 / Light and refraction

Why does a chopstick look bent in water?

The chopstick has not bent. The light has changed direction.

Start reading ↓02 / Forces and motion

Why do you lean forward when a vehicle brakes?

Objects tend to keep their existing state of motion. This property is called inertia.

Start reading ↓

Why does a chopstick look bent in water?

The chopstick has not bent. The light has changed direction.

When light travels obliquely from water into air, its speed changes and its direction usually changes too. This is refraction. We see the underwater part of a chopstick because light from it crosses the water surface and reaches our eyes.

Our brain traces incoming light back along a straight line to estimate where an object is. Refraction makes the submerged part appear shallower than it really is, so the parts above and below the surface seem misaligned.

Light travelling perpendicular to the water surface does not change direction there. The viewing angle matters: crossing between two media does not always make light bend.

Think about it: viewed obliquely from the bank, does the bottom of a pool appear deeper or shallower?

Usually shallower. This is one reason not to judge water depth by appearance alone.

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Why do you lean forward when a vehicle brakes?

Objects tend to keep their existing state of motion. This property is called inertia.

Open the inertia lab ↗

When a car moves forward, its passengers move forward too. Braking slows the car, while the body tends to keep its previous velocity. Relative to the car, the passenger therefore leans forward.

A seat belt exerts a force that slows the body. Inertia is not a force pushing someone forward; it is a property of all objects. Greater mass means greater resistance to a change in velocity.

Newton’s first law states that an object stays at rest or moves in a straight line at constant speed when the net force on it is zero. Continued motion does not require a continued push. Changing speed or direction requires a nonzero net force.

Think about it: when a stationary bus suddenly accelerates forward, which way does a standing passenger lean relative to the bus?

Backward. The feet move with the bus while the upper body tends to remain at rest. Sit securely or hold on; do not perform experiments in a moving vehicle.

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