Conservation of angular momentum

Concept — Angular momentum is conserved in the absence of external torques.

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07 · 08

Linked atoms

34 linked atoms.

06 Centre of mass

• The diver who spins
• König’s theorem for angular momentum

07 Rotational dynamics

• Case 1: inelastic collision with a hinged rod
• Case 2: elastic collision with a hinged rod
• Case 3: elastic collision with a free rod on a rail
• Disc with an unwinding rope
• Worked example — projectile against a hinged rod
• The angular-momentum exchange diagram
• Angular impulse
• The conservation law
• The skater who pulls in her arms
• The common scheme
• Problem — Disc with an unwinding rope
• Problem — Rotating disc struck tangentially
• Problem — Fantaphysics: angular momentum not conserved
• Problem — Fantaphysics: invariant moment of inertia
• Problem — The skater pulling herself in
• Problem — Reading a flat L(t) graph
• Problem — New angular velocity of a skater
• Problem — Why the skater spins faster
• Problem — Diver and pirouette
• Problem — True or false on angular momentum and inertia
• Problem — True or false on the moment of inertia
• Problem — Initial ω of a skater
• When it is conserved: the choice of pole
• Summary of the conservation laws
• Collision of a projectile with a rod

08 Universal gravitation

• Comet at perihelion and aphelion
• Conservation of angular momentum and Kepler’s second law
• Worked example: satellite, aphelion and perihelion
• Maximum and minimum distance from the central body
• Elliptical orbit — perihelion, aphelion and speed variation
• Speed of a comet at perihelion
• True or false on energy and orbits