IB Physics — Mechanics and Thermal Physics flashcards

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Themes A and B of IB Diploma Physics (first assessment 2025): kinematics, forces, momentum, energy, gas laws, thermal transfer, the greenhouse effect and circuits, with HL rigid bodies, relativity and thermodynamics.

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Learn deck · part of IB Physics · written against: IB Diploma Programme IB Physics subject guide for first assessment 2025 (themes A–E); SL and HL in one deck, HL-only cards under subtopic tags starting HL. Updated 2026-10-10.

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A cyclist speeds up uniformly from 4.0 m/s to 10.0 m/s over a distance of 30 m. What is her acceleration?

1.4 m/s² — time is not involved, so use $v^2 = u^2 + 2as$ ⁠: $a = \frac{10.0^2 - 4.0^2}{2 \times 30} = \frac{84}{60}$ ⁠.
Space Time and Motion › Kinematics
A stone is thrown straight down at 5.0 m/s from a bridge and hits the water 2.0 s later. How high is the bridge above the water? (g = 9.8 m/s²)

About 30 m — taking down as positive, $s = ut + \frac{1}{2}at^2 = 5.0 \times 2.0 + \frac{1}{2} \times 9.8 \times 2.0^2 = 10 + 19.6 = 29.6$ m.
Space Time and Motion › Kinematics
Why may the suvat equations be applied to the horizontal and vertical motion of a projectile separately, but not to its curved path as a whole?

Each component has a constant acceleration (zero horizontally, g downward vertically), which is what the suvat equations require. Along the curved path the velocity keeps changing direction, so there is no single straight line with constant acceleration.
Space Time and Motion › Kinematics
A ball is kicked from level ground at 25 m/s, 53° above the horizontal (sin 53° ≈ 0.80, cos 53° ≈ 0.60). Taking g = 10 m/s², how long is it in the air and how far away does it land?

4.0 s and 60 m. The vertical component is 20 m/s, so the flight time is $\frac{2 \times 20}{10} = 4.0$ s; the horizontal component of 15 m/s acts for 4.0 s, giving 60 m.
Space Time and Motion › Kinematics
How does air resistance change the trajectory of a projectile compared with the parabola it would follow in a vacuum?

The path becomes lower, shorter and asymmetric: the maximum height and range both fall, and the descent is steeper than the ascent because the horizontal velocity keeps dropping.
Space Time and Motion › Kinematics
What is the difference between specific heat capacity and specific latent heat?
- Specific heat capacity is the energy to raise 1 kg by 1 K with no change of phase ( $Q = mc\Delta T$ ⁠);
- Specific latent heat is the energy to change the phase of 1 kg at constant temperature ( $Q = mL$ ⁠).
Particulate Nature of Matter › Thermal Energy Transfers
Why does the temperature of melting ice stay at 0 °C even though energy is still being supplied?

The energy goes into breaking intermolecular bonds, raising the particles' potential energy rather than their mean kinetic energy, and temperature tracks only the mean kinetic energy.
Particulate Nature of Matter › Thermal Energy Transfers
How much energy turns 0.50 kg of ice at 0 °C into water at 20 °C? (Specific latent heat of fusion 3.34 × 10⁵ J/kg; c of water 4200 J/(kg·K))

About 2.1 × 10⁵ J — melting takes $0.50 \times 3.34 \times 10^5 = 1.67 \times 10^5$ J, and warming takes $0.50 \times 4200 \times 20 = 4.2 \times 10^4$ J.
Particulate Nature of Matter › Thermal Energy Transfers
A brick wall 0.10 m thick and 12 m² in area has a thermal conductivity of 0.80 W/(m·K). The temperatures on its two faces differ by 15 K. What is the rate of heat conduction through it?

1440 W — the rate is $kA\frac{\Delta T}{\Delta x} = 0.80 \times 12 \times \frac{15}{0.10}$ ⁠.
Particulate Nature of Matter › Thermal Energy Transfers
What does the Stefan–Boltzmann law give, and how is it adjusted for a real surface?

The total power radiated by a black body, $L = \sigma A T^4$ ⁠, with T in kelvin. A real surface radiates less, so the power is multiplied by its emissivity e (between 0 and 1).
Particulate Nature of Matter › Thermal Energy Transfers

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About these cards

Review status: Second-reader reviewed, with corrections applied.

Checked against:

IB Diploma Programme subject guide (topic outline only; no text copied): Physics guide for first assessment 2025, themes A and B.
OpenStax College Physics 2e, OpenStax University Physics Volumes 1–3 and OpenStax Chemistry 2e, consulted as references; no text copied.
Also checked against the IPCC Working Group I contributions to the Fifth Assessment Report (2013) and the Sixth Assessment Report (2021; CC BY-NC-ND 4.0), and the CODATA 2022 recommended values of the fundamental physical constants (reference only; no text copied).

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