Work and power (A-level only) Flashcards – AQA A-level Physics (7408)

What is the work done by a constant torque $T$ acting in the direction of rotation through an angular displacement $\theta$?

$W=T\theta$, where $\theta$ is measured in radians.

What is rotational power?

The rate of doing work.

What is the instantaneous power transferred by a torque $T$ acting in the direction of rotation at angular speed $\omega$?

$P=T\omega$, where $\omega$ is measured in radians per second.

How does frictional torque act relative to rotation?

It opposes rotation.

What energy transfer occurs when work is done against friction in rotating machinery?

Mechanical energy is transferred to thermal energy.

At angular speed $\omega$, what power is dissipated by a frictional torque of magnitude $T_f$?

$P=T_f\omega$

What must the driving torque in rotating machinery provide for?

Friction as well as any other torque required by the motion or load.