Separate two conditions
Compare zero net torque with zero net force and identify what each condition means.
AP Physics 1 · Unit 5 · Torque and Rotational Dynamics
Torque Equilibrium
Balance loads on a beam, compare rotating and static systems, and use force and torque equations to predict equilibrium.
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Learn by doing
Three ideas you’ll put into motion
Balance a beam
Change load positions and use signed torques about a useful pivot.
Analyze supports
Include beam weight, a supporting rope, and hinge forces in a complete equilibrium model.
The big idea
The key ideas, at a glance.
Rotational equilibrium allows rotation
For fixed rotational inertia, zero net external torque means constant angular velocity. The object can already be rotating.
Static equilibrium needs both balances
A system at rest remains in static equilibrium when net force and net torque are both zero. Beam weight acts at its center of gravity in uniform gravity.
A quick comparison
Balance two perpendicular downward loads on opposite sides of a pivot.
Equal opposing torques require F1d1 = F2d2.
Teaching this topic?Classroom fit, AP connections, and support
- Classroom fit
- Use for a concept introduction, guided independent practice, or a projected class discussion.
- Before students begin
- Free-body diagrams, torque, center of gravity, and force components.
- Built-in support
- Prepared scenes, guided prompts, and feedback on lesson questions.
- AP Physics 1 connections
- Unit 5: rotational equilibrium and Newton’s first law in rotational form.
- Check for understanding
- Ask why zero net torque alone does not guarantee that a system is at rest.
- Optional extension
- Try the Wall-Supported Beam lab.
Ready to test your thinking?
The first scene is set up. Start the lesson and explore.