IB DP Physics lesson pack on static and dynamic friction for Topic A.2 Forces and momentum, SL and HL, first assessment 2025. Each taught section opens with a question the class works. Editable worksheet, 53-slide lesson deck, teacher key, worked solutions and a questions-only assessment, as self-contained HTML plus colour and black-and-white PDF.
What students learn
- Friction acts along the surfaces, on both bodies, in opposite directions. Students draw the pair.
- A student’s readings show friction proportional to the normal force, unchanged by contact area or speed.
- The coefficient of friction has no unit and belongs to a pair of surfaces.
- A friction graph gives both coefficients. Static friction matches the pull up to a limit, so its law is an inequality.
- Comparing the pull with the largest static friction decides whether a body slides. If it does, dynamic friction gives its acceleration.
IB skills (Tool 3: Mathematics), all practised:
- Draw and interpret free-body diagrams.
- Resolve vectors into two perpendicular components.
- Interpret features of graphs: maxima and changes in gradient.
- Understand direct proportionality.
What’s included:
- Student Worksheet - 17 pages
- Teacher Key - 29 pages
- Worked Solutions - 19 pages
- Assessment - 13 pages
- Lesson deck - 53 slides
Seven written questions carry 72 marks across 31 parts, plus five multiple-choice items. The class works Questions 1 to 4, worth 38 marks, then an exit ticket. Students draw force arrows on five of the nine figures. In Question 3 a chair is pulled with 19 N against a limit of 19.6 N, so the friction is 19 N, not 19.6 N. That settles one of two opening votes. In Question 4 a truck pulls away and the friction on its loose crate points forwards.
The slope and the angled push are exam practice, outside the taught hour. So is a 10-mark challenge: a block on a trolley. Students find the largest pull before the block slides, then both accelerations. A Nature of Science box treats the law as the pattern in Question 1’s readings. SI units, IB notation and IB command terms throughout. Use it with grades 11-12 (ages 16-19) as a lesson, cover lesson, homework or revision.
Part of the A.2 Forces and Momentum Complete Unit Bundle, 30% off buying the packs separately.
Related resources:
- Newton’s Second Law: F = ma, the lesson before this one
- Free-Body Diagrams and Force Pairs, where those diagrams are taught
- Upthrust, Viscous Drag and Terminal Velocity, the lesson that comes next
- Resultant Force, Inertia and Newton’s First Law, where zero resultant force is taught
Updated 12 Nov 2026: please reprint.
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