University Physics I · Angular Momentum · 11.01
Angular momentum of a particle
Position cross momentum, origin dependence, direction, and orbital examples.
Build the model
Connect the measurement to the mechanism.
Position cross momentum, origin dependence, direction, and orbital examples. Treat this course-map statement as a claim to test rather than an invitation to import a familiar equation. In Angular Momentum, begin from origin selection, then state the system, observable, assumptions, and evidence before calculating.
- Simple definition
- Position cross momentum, origin dependence, direction, and orbital examples.
- Example
- A strong response uses position-momentum vector diagrams and states where the model stops being reliable.
Its direction follows the right-hand rule.
r is measured from the chosen origin.
Only velocity perpendicular to r contributes.
θ is the angle from r to v.
The subsection's claim
Position cross momentum, origin dependence, direction, and orbital examples.
How to work with it
Start from origin selection. Then choosing an origin and identifying external torque before asserting conservation. Select an equation only after its variables and assumptions match the stated system.
What evidence would decide
Is angular momentum conserved when a rotating system changes its mass distribution? Useful evidence includes angular-speed and geometry data, inertia model, before-after comparison, and friction estimate.
Keep the boundary visible
This GioPhysics course map is an adaptable teaching sequence, not a claim of accreditation or a universal university syllabus. Departments can adjust the order, mathematical depth, laboratory hours, and optional fluids endpoint to match local requirements. A result should be checked against units, signs, limiting cases, and the conditions under which its model was derived.
Change one variable at a time
Make the relationship visible.
Rotate velocity. Angular momentum vanishes for radial motion and is largest when velocity is perpendicular to r.
|L|1.60 kg m²/s
PERPENDICULAR SPEED4.00 m/s
Live interpretation|L|: 1.60 kg m²/s. PERPENDICULAR SPEED: 4.00 m/s
Catch the common trap
Explain before calculating.
When is a particle's angular momentum about an origin zero?
Choose an answer to test the model.
Practice & worked examples
Reason from the model, then test the result.
Worked calculationA 0.250 kg particle is 0.400 m from the origin and moves at 6.00 m s⁻¹ perpendicular to r. Find |L|.
- Use |L|=mrv sinθ.
- Here θ=90°, so sinθ=1.
- |L|=(0.250)(0.400)(6.00)=0.600 kg m² s⁻¹.
AnswerThe angular-momentum magnitude is 0.600 kg m² s⁻¹; r×v sets its direction.
TransferDesign one observation that separates Angular momentum of a particle from Angular momentum of a rigid body.
- Name the observable central to Angular momentum of a particle.
- Name the contrasting observable or condition in Angular momentum of a rigid body.
- Choose a graph feature, sign, scale, or limiting case that would distinguish them.
AnswerThe comparison is useful only if the proposed observation could rule out at least one of the two accounts.