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Angular Momentum

Physics: AQA A Level, topic 11.1.5

Angular momentum

Angular momentum must be conserved.

Calculating angular momentum

Calculating angular momentum

  • The equation for angular momentum is:
  • angular momentum = angular velocity x moment of inertia
  • L=ωIL={\omega}I
  • Where L is the angular momentum.
Conservation of angular momentum

Conservation of angular momentum

  • If an ice skater draws in their arms they spin faster.
  • If they draw in their arms they decrease their moment of inertia.
  • As angular momentum must be constant and the moment of inertia has decreased the angular velocity must increase.

Angular Impulse

Angular impulse is the same as a linear impulse but it acts to turn an object.

Angular torque

Angular torque

  • The equation for torque is:
  • Torque = the rate of change of angular momentum
  • τ=ΔLΔt\tau=\frac{{\Delta}L}{{\Delta}t}
  • Where τ\tau is the torque.
Angular impulse

Angular impulse

  • The equation for angular impulse is:
  • Impulse = torque x time
  • J=τtJ={\tau}t
  • Where J is the angular impulse.

Test yourself on Angular Momentum

  • What is the correct equation for angular momentum?

  • Increasing the moment of inertia will have what effect on the angular momentum?

  • What is the equation for angular torque?

  • What is the equation for angular impulse?

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