The Ultimate Guide to the IB Physics IA: 50+ Topic Ideas & Pro Tips

Hey there! Let's talk about the IB Physics Internal Assessment, or as it's now officially called, the "Scientific Investigation". This is your chance to be a real physicist—designing an experiment, collecting data, and analysing it all on your own. It's a big part of your final grade (worth 24 marks), and honestly, choosing a great topic is half the battle won.

This guide is designed to walk you through everything, from understanding the new 2025 assessment criteria to brainstorming a topic that's both interesting and high-scoring. Let's dive in.

First Things First: Understanding the New (2025) Assessment Criteria

Before you even think about topics, you need to know what the examiners are looking for. The game has changed for exams from May 2025 onwards! The old rubric is out, and a new, streamlined set of four criteria is in, with each worth 6 marks.

How to Choose Your IA Topic: A Strategic Framework

A good topic is a balance between what interests you and what's practical. Don't just pick the first thing you see online. Think like a physicist.

Key Considerations for a Winning Topic:

• Personal Interest: Seriously, pick something you find cool. You'll be spending a lot of time on this. If you love sports, music, or even video games, try to find the physics in them.
• Feasibility: Can you actually do this experiment with the equipment in your school lab? Avoid anything that needs a particle accelerator. Keep it simple enough to be completed well within the 10-hour timeframe. A simple idea executed perfectly beats a complex one done poorly.
• Clear, Measurable Variables: Your experiment must have one thing you can change (the independent variable) and one thing you can measure as a result (the dependent variable). Both must be quantifiable and so "Type of material" is a weak independent variable; "thickness of material in mm" on the other hand, is a strong one.
• Strong Link to Physics Theory: Your investigation must allow you to discuss and apply concepts from the IB Physics syllabus. However, you do not need to limit yourself to the syllabus.

The "How does X affect Y?" Brainstorming Method

This is the most reliable way to frame a research question. Think about a cause-and-effect relationship you can test.

Crafting the Perfect Research Question

Once you have an idea, you need to turn it into a focused research question. It's the compass for your entire investigation. Stick to this format:

"How does the [Independent Variable (X)] affect the [Dependent Variable (Y)] of a [Specific system or context]?"

Example of a great research questions: "How does the temperature of a tennis ball affect its coefficient of restitution when dropped from a constant height?"

The Inspiration List: 50+ IB Physics IA Ideas

Stuck for ideas? Use this list as a starting point. Remember to add your own personal twist to make your investigation unique. Always check with your teacher to ensure your idea is feasible.

Mechanics

• How does the launch angle of a projectile affect its horizontal range?
• How does the cross-sectional area of a falling coffee filter affect its terminal velocity?
• How does the angle of an inclined plane affect the acceleration of a rolling object?
• Investigating the relationship between the period of a simple pendulum and its length.
• How does the mass suspended from a spring affect its period of oscillation?
• How does the internal pressure of a basketball affect its rebound height?
• Investigating how the centripetal force on a rotating object is affected by its angular velocity.
• Determining the coefficient of static friction between two surfaces with varying normal force.

Thermal Physics

• How does the surface area to volume ratio of a container affect the cooling rate of hot water?
• Investigating how the thickness of an insulating material affects the rate of heat loss.
• How does the salinity (salt concentration) of water affect its specific heat capacity?
• How does the temperature of a liquid (e.g., motor oil) affect its viscosity?
• Verifying Charles's Law: How does the temperature of a gas affect its volume at constant pressure?
• How does the colour of a surface affect its rate of thermal energy absorption?

Waves & Oscillations

• How does the tension in a guitar string affect the frequency of the sound it produces?
• Investigating the relationship between the length of a closed air column and its resonant frequency.
• How does the depth of water in a tray affect the speed of surface waves?
• How does the concentration of sugar in a solution affect its refractive index?
• Determining the wavelength of a laser using a diffraction grating.
• Investigating Malus's Law: How does the angle between two polarising filters affect the intensity of transmitted light?

Electricity & Magnetism

• How does the length of a nichrome wire affect its electrical resistance?
• How does the temperature of a conductor affect its resistance?
• Investigating how the number of coils in a solenoid affects the strength of its magnetic field.
• How does the temperature of a battery affect its internal resistance?
• How does the distance from a light source affect the voltage output of a solar cell?
• Investigating the time constant of a discharging RC circuit by varying the resistance.
• How does the speed of a falling magnet through a coil affect the magnitude of the induced EMF?

Modern & Quantum Physics

• Investigating the inverse square law for gamma radiation using a G-M counter.
• How does the thickness of a shielding material (e.g., aluminium foil) affect the absorption of beta radiation?
• Determining Planck's constant using the turn-on voltage of different coloured LEDs. (A classic but solid choice).

Level Up: Unique IA Ideas to Show Personal Engagement

Want to stand out? Try adding a unique variable or combining different areas of physics. This is where you can really show your creativity.

• The Magnus Effect: How does the spin rate of a ball affect its trajectory? (Combines Mechanics & Rotational Dynamics).
• Damped Oscillations: How does the viscosity of a liquid (e.g., water, oil, glycerine) affect the damping of an oscillating pendulum? (Combines Mechanics & Fluid Dynamics).
• Sports Science: How does the temperature of a squash ball affect its coefficient of restitution? (Combines Mechanics & Thermal Physics).
• Musical Physics: How does the humidity of the air affect the speed of sound, measured using resonance in a tube? (Combines Waves & Thermal Properties).
• Material Science: How does temperature affect the Young's modulus of a plastic ruler? (Combines Mechanics & Thermal Physics).