The Top 12 Paper 2 Definition-Style Questions

Continuing my thoughts from the previous blog post, I put together a list of twelve definition-style questions that have come up on IB Physics exams over the past years. 

This idea came out from a chat with a student whom I tutor, because while he loves calculations, he really does not enjoy questions where he needs to explain concepts. So if you are in the same shoes, you can simply understand and memorize the twelve explanations below and hopefully get some definition marks on Paper 2. Of course, this list does not cover all possibilities, but it gives you a good starting point with a minimum amount of effort. The topics in all twelve questions are part of both the SL and the HL syllabus.

Enjoy 🙂

Question 1: Newton’s third law. [usually 2 marks]

• Note: the application of this law comes up in different contexts, but the key points you need to include are basically always the same. 
• Key points to include in your answer:
• When object A exerts a force on object B, object B also exerts a force on object A.
• The two forces have the same magnitude and point in opposite directions.
• Note: make sure that you give your explanation in the context of the question, specifically referring to the two objects that exert the forces on each other.

Question 2: Describing the motion of the particle when a force acts on it. [3 marks]

• Note: often comes up in the context of fields, so for example, a negatively charged particle is held near an electron and then released. 
•  Key points to include in your answer:
• Direction in which the particle moves.
• Speed increases/decreases.
• Acceleration increases/decreases.

Question 3: Showing that a collision is elastic/inelastic. [3 marks]

•  Key points to include in your answer:
• Calculate the kinetic energy before the collision.
• Calculate the kinetic energy after the collision.
• Compare the two kinetic energy values. If they are the same, the collision is elastic. If the kinetic energy before is greater than the kinetic energy after the collision, it is inelastic. 

Question 4: Describing the internal energy of a substance at the same temperature, but in two different states (solid/liquid/gas). [2 marks]

• Key points to include in your answer:
• Temperature is the same, so the kinetic energy of the particles is the same.
• A different state means that the particles have different intermolecular potential energies (highest in a gas, then in a liquid, then lowest in a solid).
• Internal energy is the sum of the kinetic energy and intermolecular potential energy, so it is highest in a gas, then in a liquid, and lowest in a solid. 

Question 5: The greenhouse effect. [2 or 3 marks]

• Key points to include in your answer:
• The radiation from the surface of the Earth is in the infrared region of the electromagnetic spectrum.
• As a result, greenhouse gases in the atmosphere absorb this radiation due to resonance. 
• The greenhouse gases then reradiate this absorbed radiation in all directions.
• Note: questions on exams might be asked in slightly different ways/in different contexts.

Question 6: Kinetic model of an ideal gas. [1 to 3 marks]

• Note: the assumptions of the kinetic model show up in questions in different ways, so aim to remember the key points of this model and apply them depending on the context of the question. 
• Key assumptions of the kinetic model:
• The gas consists of identical point particles.
• The volume of the particles is negligible (compared with the volume of the gas).
• There are no intermolecular forces between the gas particles.
• All collisions are elastic.
• The duration of the collisions is negligible when compared with the time between collisions.

Question 7: Transverse/longitudinal wave definition. [1 mark]

•  Key points to include in your answer:
• Transverse wave: the direction of oscillations is perpendicular to the direction of wave propagation/energy transfer.
• Longitudinal wave: the direction of oscillations is parallel to the direction of wave propagation/energy transfer.

Question 8: The formation of a double-slit diffraction pattern. [2 or 3 marks]

•  Key points to include in your answer:
• The waves that emerge from the slits interfere/superpose.
• When the waves arrive at the screen in phase, there is constructive interference, so a bright fringe forms on the screen.
• When the waves arrive at the screen 180 degrees out of phase, there is destructive interference, so a dark fringe forms on the screen.
• Note: you can also refer to the constructive/destructive interference formula in your answer. These can be found in Topic C.3.

Question 9: Outlining how a standing wave is formed on a string/in a pipe. [2 marks]

•  Key points to include in your answer:
• The incoming wave is reflected.
• The incoming and the reflected waves superpose.
• Note: it is a good idea to adapt the above definition to the context of the question (string, pipe, etc).

Question 10: Difference between travelling and standing waves. [1 or 2 marks]

• Key points to include in your answer:
• For a travelling wave amplitude is constant, for a standing wave amplitude varies.
• A travelling wave transfers energy, a standing wave does not transfer energy.
• Travelling waves do not have nodes/antinodes, standing waves have nodes/antinodes.

Question 11: Binding energy of a nucleus. [1 mark]

• Key points to include in your answer:
• The energy that is released when a nucleus is formed from its individual nucleons. OR The energy required to completely separate the nucleons of a nucleus.

Question 12: Evolutionary path of a star. [2 marks]

• Key points to include in your answer:
  • Red giant → planetary nebula → white dwarf.
  • Red supergiant → supernova explosion → neutron star.
  • Red supergiant → supernova explosion → black hole.
• Low mass stars (less than 10 solar masses)
• Moderate mass stars (between 10 and 30 solar masses)
• Large mass stars (more than 30 solar masses)