IB Physics IA Ideas: 30 Research Questions

The best Physics IA questions name two variables you can measure and a relationship you can predict. Searching for Physics IA ideas tends to return topic names, which are not enough, so here are 30 original research questions in the five themes of the current course, each with the variables, the level of apparatus and the pitfall most likely to hurt. They are starting points. Your own question, your own method and your own data are what will be assessed, so change something: a material, a range or a setting.

How to use these questions

Check what your school hasMatch the apparatus level to what your lab can offer. Where we mention radiation or lasers, follow your school's safety rules and your teacher's instructions.
Plan at least five valuesA wide range of the independent variable, each repeated, gives your analysis something real to work with.
Predict the relationshipYou will compare your result with accepted physics, so pick questions where you can predict a trend, a gradient or a limit.
Add your twistA different surface, liquid, range or setting turns a standard experiment into your own.
Run a quick trialTry one rough run to see if the measurements are stable before you commit.

Small-group work is allowed on the current course if each student changes a different independent or dependent variable, the data is unique to each student and each of you writes an individual report. The report is limited to 3,000 words, and the IA takes about 10 hours.

Theme A. Space, time and motion (mechanics)

1. How does the release height of a trolley on a ramp affect its speed at the bottom, and how much energy is lost to friction? Variables: IV release height; DV speed; control ramp angle, trolley mass, surface. Apparatus: Standard: light gates or video analysis. Watch out for: assuming a frictionless ramp; too few heights.
2. How does the amplitude of a pendulum affect its period, and at what angle does the small-angle approximation stop working? Variables: IV amplitude; DV period; control length, bob mass. Apparatus: Basic: stopwatch and protractor, or video. Watch out for: timing one swing; starting angles that are all small.
3. How does the mass hung on a spring change its oscillation period, and how does the spring's own mass matter? Variables: IV hanging mass; DV period; control amplitude, spring. Apparatus: Basic to standard. Watch out for: ignoring the spring's mass; too narrow a mass range.
4. How does the shape of a falling paper cone affect its terminal speed? Variables: IV base area or cone angle; DV terminal speed; control mass, drop height. Apparatus: Basic: ruler and video. Watch out for: never reaching terminal speed; air currents in the room.
5. How does the angle at which a ball is launched affect its range, and does the best angle change with launch height? Variables: IV launch angle; DV range; control launch speed. Apparatus: Standard: launcher and video tracking. Watch out for: an inconsistent launch speed; reading landing points by eye.
6. How does the coefficient of friction between a block and a surface change with the type of surface and the normal force? Variables: IV surface or added mass; DV friction coefficient; control speed of pull. Apparatus: Standard: force sensor. Watch out for: reading static and kinetic friction as the same; uneven surfaces.

Theme B. The particulate nature of matter

7. How does the temperature of water affect the time it takes to cool, and how well does Newton's law of cooling fit? Variables: IV starting temperature; DV cooling rate; control volume, container. Apparatus: Basic to standard: thermometer or data logger. Watch out for: heat loss from the thermometer; stopping before the room temperature is reached.
8. How does the pressure of a trapped gas change with volume at fixed temperature? Variables: IV volume; DV pressure; control temperature, amount of gas. Apparatus: Standard: syringe and pressure sensor. Watch out for: leaks; heating during compression.
9. How does the specific heat capacity of a metal block compare with accepted values? Variables: IV energy supplied; DV temperature rise; control mass, insulation. Apparatus: Standard: heater and joulemeter. Watch out for: heat loss to the surroundings; poor thermal contact.
10. How does the concentration of salt in water affect the time to melt a block of ice? Variables: IV salt concentration; DV melting time; control ice mass and temperature. Apparatus: Basic. Watch out for: uneven ice blocks; unmeasured room heating.
11. How does the length of a metal wire affect its resistance, and does temperature matter? Variables: IV length; DV resistance; control cross-section, current level. Apparatus: Standard: ammeter and voltmeter. Watch out for: wire heating at high current; contact resistance at clips.
12. How does the thickness of an insulating layer affect the rate of heat loss from a hot can? Variables: IV thickness; DV cooling rate; control starting temperature. Apparatus: Basic to standard. Watch out for: gaps in the insulation; draughts.

Theme C. Wave behaviour

13. How does the length of a vibrating string affect its frequency, and does tension change the pattern? Variables: IV length; DV frequency; control tension, string. Apparatus: Standard: tuner app or frequency generator. Watch out for: wrong frequency read from background noise; changing tension by accident.
14. How does the depth of water in a ripple tank affect wave speed? Variables: IV depth; DV wave speed; control frequency. Apparatus: Standard: ripple tank and strobe or video. Watch out for: stray reflections; small depth range.
15. How does the width of a single slit affect the width of the diffraction pattern from a laser? Variables: IV slit width; DV central maximum width; control distance to screen. Apparatus: Standard: laser and slit set. Watch out for: safety with lasers; reading the edge of a bright spot.
16. How does the length of an air column affect the resonant frequencies in a tube closed at one end? Variables: IV column length; DV resonant frequency; control temperature. Apparatus: Standard: tube and tuning fork or speaker. Watch out for: end correction ignored; background noise.
17. How does the distance between a sound source and a microphone affect the measured loudness? Variables: IV distance; DV sound level; control source volume. Apparatus: Basic: phone app. Watch out for: echoes in the room; an app with an uncalibrated microphone.
18. How does the angle of incidence affect the refracted angle in different transparent materials, and how close is the result to Snell's law? Variables: IV angle of incidence; DV angle of refraction; control material, wavelength. Apparatus: Basic to standard. Watch out for: reading angles from thick beams; too few materials or angles.

Theme D. Fields

19. How does the distance between two magnets affect the force between them? Variables: IV separation; DV force; control orientation, magnet pair. Apparatus: Standard: balance or force sensor. Watch out for: the magnets not being point-like; stray magnetic materials nearby.
20. How does the current in a coil affect the strength of the magnetic field at its centre? Variables: IV current; DV field; control coil, position. Apparatus: Standard: magnetic field sensor. Watch out for: coil heating; Earth's field as a hidden offset.
21. How does the number of turns in a solenoid affect the magnetic field inside it? Variables: IV turns; DV field strength; control current, length. Apparatus: Standard. Watch out for: changing coil length while changing turns; heating.
22. How does the time for a capacitor to discharge depend on the resistance and capacitance? Variables: IV resistance or capacitance; DV time constant; control starting voltage. Apparatus: Standard: voltmeter and data logger. Watch out for: meter resistance affecting the circuit; using one value for tolerance.
23. How does the speed of a magnet falling through a copper tube compare with free fall? Variables: IV magnet strength or tube thickness; DV fall time; control height. Apparatus: Basic to standard. Watch out for: the magnet touching the tube wall; timing by hand.
24. How does the electrical output of a small solar cell change with the angle of the light? Variables: IV angle; DV voltage or current; control distance, light source. Apparatus: Standard. Watch out for: stray light; the light source output changing as it warms.

Theme E. Nuclear and quantum physics

25. How does the threshold voltage of different coloured LEDs relate to the wavelength of their light, and what value of Planck's constant results? Variables: IV LED colour (wavelength); DV threshold voltage; control temperature. Apparatus: Standard: voltmeter, resistor, spectrometer or known wavelengths. Watch out for: judging when the LED just glows; a wide spread of wavelength in one LED.
26. How does the absorption of light by a filter or dye change with its thickness or concentration? Variables: IV concentration or thickness; DV transmitted intensity; control light source. Apparatus: Standard: light sensor. Watch out for: stray light; light source drifting.
27. How does the count rate from a sealed school source change with distance, and does it follow an inverse-square trend? Variables: IV distance; DV count rate; control time of counting. Apparatus: Advanced: Geiger counter, teacher-supervised; or use simulation or published data. Watch out for: background radiation; counting too few events; strict school safety rules.
28. How does the thickness of a material affect the transmission of radiation, and what absorption coefficient results? Variables: IV thickness; DV count rate; control source distance. Apparatus: Advanced: supervised, or use a dataset. Watch out for: background; the safety of the source; materials of uneven density.
29. How does a simulated radioactive decay with dice or coins match the exponential law? Variables: IV number of dice; DV counts per round; control rules. Apparatus: Basic: dice or coins. Watch out for: too few dice, giving a noisy result; mixing up chance and decay constant.
30. How does the stopping voltage in a photoelectric simulation depend on the frequency of light, and what does it say about work function? Variables: IV frequency; DV stopping voltage; control metal. Apparatus: Basic: computer simulation. Watch out for: treating simulation output as real data without acknowledging it; too few frequencies.

Pitfalls that apply to almost every idea

Too few values, or a range so narrow that the trend is invisible.
Controlled variables listed but not measured or monitored.
Uncertainty worked out once and then forgotten in the graph and the conclusion.
Treating a simulation as an experiment without saying so.
A conclusion that says more than the data shows.

When you have chosen, read how the work is judged in Physics IA criteria explained. The main Physics IA guide has the overview. Writing an Extended Essay in physics too? See Extended Essay topics and research questions for the difference between an experiment and a research essay.

IB Physics IA ideas: 30 research questions