IB DP Physics (2025) A2.9 Centripetal Acceleration

IB DP Physics circular motion lesson pack: angular velocity and centripetal acceleration, Topic A.2 Forces and momentum, SL and HL, first assessment 2025: why a body going round a circle at constant speed is still accelerating. Editable worksheet, 57-slide lesson deck, teacher key, worked solutions and a questions-only assessment, supplied as self-contained HTML plus colour and black-and-white PDF.

What students learn

• Uniform circular motion: a constant speed, a turning velocity, and so an acceleration.
• Period, frequency and angular velocity in rad s⁻¹.
• v = ωr = 2πr/T, shown by the class from the length of an arc.
• Why the acceleration points to the centre, from its parts along and across the velocity.
• Centripetal acceleration a = v²/r = ω²r = 4π²r/T², choosing the form that suits the quantities given.

IB skills (Tool 3: Mathematics, with Inquiry 3: Concluding and evaluating):

• Select and manipulate equations (practised).
• Calculate with ratios, reciprocals, exponents and trigonometric ratios (practised).
• Express derived units in terms of SI units (practised).
• Linearize graphs, only where appropriate (practised).
• Interpret the gradient and intercept of a graph (practised).
• Propagate uncertainties in processed data (practised).
• Draw and interpret uncertainty bars (practised).
• Identify and discuss random and systematic errors (practised).

What’s included:

• Student Worksheet - 18 pages
• Teacher Key - 32 pages
• Worked Solutions - 18 pages
• Assessment - 13 pages
• Lesson deck - 57 slides

Nine structured questions and five multiple-choice items: 57 marks across 30 parts, and nine figures, two with answer layers stripped from the student copy, not hidden. Six questions, 26 marks, are worked in the room; the rest go home, including a ten-mark data question in the Paper 1B pattern: a phone on a turntable, a radius from a linearized graph and a systematic error to explain.

It opens on a merry-go-round and a class vote: is the child accelerating? It describes the motion only: centripetal force is not covered. Radians and arc length sit in two margin boxes. Worksheet and deck open in any modern browser with nothing to install, and the worksheet is fully editable. SI units, IB notation and IB command terms throughout. Suitable for grades 11-12 (ages 16-19) as a lesson, cover lesson, homework or revision.

Related resources:

• Acceleration and Non-Uniform Motion, where acceleration is defined
• Topic A.2 Test: Forces and Momentum, the topic test
• Uncertainties on a Graph, the skill pack behind the data question
• The Units of a Quantity, base and derived units (free)

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