The core ideas include motion equations such as , energy equations such as , wave relationships such as , and circuit laws such as . Fields are described using force per unit mass or charge, such as and . Atomic and quantum equations connect photon energy to frequency using .
Most IB problems require choosing the correct model, checking units, and applying the equation only under its valid assumptions.
Key Facts
- For constant acceleration, the kinematics equations include , , and .
- Newton's second law is , where the net force causes acceleration of a mass .
- Kinetic energy is , and gravitational potential energy near Earth's surface is .
- Power is the rate of energy transfer, so , and mechanical power can also be written as when force and velocity are parallel.
- The wave equation is , where is wave speed, is frequency, and is wavelength.
- For an ideal gas, , and the average translational kinetic energy per molecule is .
- Ohm's law is , electric power can be calculated using , , or .
- Photon energy is , linking quantum energy, frequency, and wavelength.
Vocabulary
- Net force
- The vector sum of all forces acting on an object, which determines its acceleration through .
- Work
- Energy transferred by a force acting through a displacement, calculated as .
- Specific heat capacity
- The energy required to raise the temperature of of a substance by , given by .
- Frequency
- The number of wave cycles passing a point per second, measured in hertz and related to period by .
- Electric field strength
- The force per unit positive charge at a point in a field, defined by .
- Photon
- A packet of electromagnetic radiation with energy .
Common Mistakes to Avoid
- Using kinematics equations when acceleration is not constant, which is wrong because equations such as assume uniform acceleration.
- Confusing mass and weight, which is wrong because mass is measured in kilograms while weight is a force calculated by .
- Forgetting that temperature in gas equations must be in kelvin, which is wrong because only works with absolute temperature .
- Mixing up wavelength and frequency in , which is wrong because increasing frequency decreases wavelength when wave speed stays constant.
- Using for non-ohmic components without checking the graph or conditions, which is wrong because resistance may change with temperature or voltage.
Practice Questions
- 1 A car accelerates uniformly from to in . Find its acceleration using .
- 2 A object moves at . Calculate its kinetic energy using .
- 3 A wave has frequency and wavelength . Calculate its speed using .
- 4 A student wants to use for a gas sample whose temperature is given in degrees Celsius. Explain what must be done first and why.
Understanding IB Physics Data Booklet Key Equations Reference
A data booklet is most useful when it helps you describe a physical situation before you calculate anything. Start by identifying the system. This might be a falling object, a gas in a container, a charged particle, or a circuit component.
Decide what enters and leaves the system, and which quantities can change. A sketch often exposes the right model. Draw force arrows for mechanics, energy stores for transfers, ray paths for optics, or current paths for circuits.
Then label known values with units. This prevents a common error where a correct equation is used for the wrong physical process.
Many equations contain conditions that are easy to miss. The constant acceleration relationships only work when acceleration stays unchanged over the time interval. Near Earth, the usual gravitational potential energy model assumes that the change in height is small compared with Earth’s radius.
An ideal gas model works best when particles are far apart and their own volume has little effect. In circuits, the resistance of a filament lamp changes as it heats, so its current and voltage are not simply proportional. Learning these limits matters because an answer can look numerically reasonable while being physically invalid.
Units provide one of the fastest checks in physics. Convert prefixes before inserting numbers. A millisecond is one thousandth of a second, while a megahertz is one million hertz.
Keep values in standard SI units unless the question clearly supports another choice. Check the final unit against the quantity requested. Energy should end in joules, power in watts, pressure in pascals, and electric charge in coulombs.
Dimensional checks can reveal missing squares, incorrect rearrangements, or confusion between quantities such as mass and weight. Significant figures matter too. A result should normally match the precision of the measurements used.
Students meet these ideas outside the classroom more often than it may seem. Braking distance depends on changes in kinetic energy and the work done by friction. Household electricity bills measure energy transferred over time, which links power ratings to everyday appliance use.
Sound from speakers, radio signals, and light from screens all involve frequency and wavelength. Thermal equations help explain tyre pressure changes on hot days and why a sealed container can become dangerous when heated. Quantum equations connect to LEDs, solar cells, and medical imaging.
During practice, focus less on memorising isolated formulas. Practice stating what each symbol means, the assumptions behind the model, and whether the result has a sensible size and direction.