Practise: Rotational Motion independent problems
Work through one constructed H3 Rotational Motion problem for each objective, a multi-stage synthesis problem and worked-error diagnosis. Each new attempt can draw different problems.
Learning goals
- Work through the questions and use the feedback to plan revision.
Practise
Work through the questions in any order. Check a response when you are ready to see the marking guidance. Use the feedback to decide what to practise next; this does not prove mastery.
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Beyond the syllabus: optional enrichment that does not count towards your progress.
About this activity
Six structured Rotational Motion problems with five labelled written-response fields per problem.
H3 Physics 9814 · Constructed practice
Attempt one problem from every objective family without opening the worked solution. Define the system and axis, state assumptions and a positive direction, show the governing stages, include units and a sanity check, then interpret the physics.
These problems are practice: they are marked against reviewed rubrics but do not change your course progress. Use the Rotational Motion checks to check your progress, repair what needs work and return for a later review.
Six objective problem families
The practice above gives one constructed-response problem for each objective, chosen from two written for it, so a new attempt can give you different problems. Your responses are marked against reviewed rubrics, with feedback as you go. The synthesis problem below supplements these families; it does not replace any of them.
- H3-ROT-01: Use angular displacement, velocity and acceleration for fixed-axis rotation.
- H3-ROT-02: Apply constant-angular-acceleration equations with a consistent sign convention.
- H3-ROT-03: Calculate moments of inertia using integration and the parallel-axis theorem.
- H3-ROT-04: Relate torque to the rate of change of angular momentum.
- H3-ROT-05: Derive and apply rotational kinetic energy.
- H3-ROT-06: Combine translation and rotation to analyse rolling without slipping.
H3-ROT-SYNTHESIS-01
Remote sampler deployment
An unfamiliar remote sampler uses a rigid drum of moment of inertia 1.50 kg m². A motor applies 8.00 N m while its bearing supplies an opposing 2.00 N m torque for 4.00 s from rest. Choose the system, axis and model. Determine the angular acceleration, angular speed and rotational kinetic energy after 4.00 s. No method labels are supplied in the working space.
View three-stage worked solution
- System and axis
- System: drum about its fixed shaft axis.
- Assumptions
- The drum is rigid, I is constant and both torques are constant during the interval.
- Representation
- Draw both torque arrows about the shaft and a three-stage map from net torque to angular response to energy.
- Sign convention
- Take the motor torque as positive.
- Stages
- Στ = 8.00 − 2.00 = 6.00 N m and α = Στ/I = 4.00 rad s⁻².
- From rest, ω = αt = 16.0 rad s⁻¹.
- Krot = ½Iω² = ½(1.50)(16.0)² = 192 J.
- Check
- Torque work Στθ gives θ = ½αt² = 32 rad and W = 6.00(32) = 192 J, independently matching the energy result.
- Interpretation
- The net external torque increases angular momentum; its work appears as rotational kinetic energy.
H3-ROT-ERROR-01
Audit a hatch calculation
A 12.0 N force acts 0.500 m from a hatch pivot at 30° to the position vector. The student's solution is: (1) choose the hatch as system and anticlockwise positive; (2) draw r from pivot to the force point; (3) τ = Fr = 6.00 N m; (4) α = τ/I. Locate the first invalid step, correct it and explain the physical consequence if I = 0.750 kg m².
View the first decisive error and correction
Step 3 is the first invalid step. Torque uses the perpendicular force component: τ = rF sin 30° = 0.500(12.0)(0.5) = 3.00 N m, not 6.00 N m. Therefore α = 3.00/0.750 = 4.00 rad s⁻². The student's result would double both the torque and the predicted angular acceleration by treating the whole force as perpendicular.
Check again
After focused repair, return without looking back. The next check changes the structure or physical setting, so apply the method independently rather than recalling the first answer. Feedback follows your response.
Course and syllabus information
- Course
- GCE A-Level H3 Physics
- Edition
- GCE A-Level H3 Physics 2027