Angular momentum (A-level only) Flashcards – AQA A-level Physics (7408)

What is the angular momentum of a body rotating about a fixed axis, in terms of its moment of inertia and angular velocity?

$L = I\omega$

What does moment of inertia describe for a body rotating about a fixed axis?

How its mass is distributed relative to the axis.

What does angular velocity describe?

The rate and direction of rotation.

What are the SI units of angular momentum?

$\mathrm{kg\,m^2\,s^{-1}}$

Under what condition is a system’s total angular momentum conserved?

When the resultant external torque is zero.

For rotation about a fixed axis, what equation relates the initial and final moments of inertia and angular velocities when angular momentum is conserved?

$I_1\omega_1 = I_2\omega_2$

When angular momentum is conserved, how does changing the moment of inertia affect the magnitude of angular velocity?

A decrease in moment of inertia increases angular velocity’s magnitude; an increase decreases it.

What is angular impulse?

The change in angular momentum produced by a torque acting over a time interval.

For a constant resultant torque $T$ acting for time $\Delta t$, what equation relates torque, time and angular momentum?

$T\Delta t = \Delta L = \Delta(I\omega)$

What is the direction of the change in angular momentum produced by a resultant torque?

The direction of the resultant torque.