IB DP Physics (2025) A3.4 Conservation of Mechanical Energy

IB DP Physics conservation of mechanical energy lesson pack, Topic A.3 Work, energy and power, SL and HL, first assessment 2025: the energy method, a speed or a height from Ek + Ep + EH without the direction or the time, and suvat as the check. Editable worksheet, 63-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

• Mechanical energy as Ek + Ep + EH, conserved when no frictional or resistive force acts and only weights and springs do work.
• Ek + Ep shown to stay the same when only the weight does work, whatever the path.
• Why the energy method still works where v² = u² + 2as cannot: a twisting slide, a spring, a swing.
• The work done by a weight or a spring as energy transformed between forms, and none by a force at right angles to the motion.

IB skills (Tool 3: Mathematics):

• Select and manipulate equations (practised).
• Use arithmetic and algebra to solve problems (practised).
• Derive relationships algebraically (practised).
• Determine the effect of changing one variable on another (practised).
• Draw and interpret uncertainty bars (practised).
• Interpret the gradient and the intercept of a graph (practised).

What’s included:

• Student Worksheet - 20 pages
• Teacher Key - 32 pages
• Worked Solutions - 21 pages
• Assessment - 16 pages
• Lesson deck - 63 slides

Eight structured questions and four multiple-choice items: 61 marks across 33 parts, and eleven figures, one with an answer layer stripped from the student copy, not hidden. Five questions, 34 marks, are worked in the room, between two opening votes and a multiple-choice exit ticket. The rest go home, including two exam-style questions and a ten-mark data question in the Paper 1B pattern: a load released on a spring, with a zero error and uncertainty bars.

Every system is idealised, with no friction or air resistance: resistive forces, power and efficiency are left to later lessons. The three energy formulas are recalled, not taught. 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:

• Gravitational and Elastic Potential Energy, the lesson before this one
• SUVAT Equations II: Vertical Motion and Gravity, where vertical throws are solved by suvat
• Proportionality and Scaling, the skill pack behind the prediction questions
• Measuring the Acceleration of Free Fall, where uncertainty bars are taught (free)

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