# Torque $\vec \tau$

How hard something is being turned; the cause of changes in angular motion; the cause of angular acceleration.

$$\vec \tau=\vec r\times \vec F$$

$\vec r$ is the position vector from the axis-of-rotation and $\vec F$ the force. Numerically, only the perpendicular components are multiplied: $$\tau=r\,F_\perp=r_\perp\,F$$

• Vector property
• Symbol: $\vec \tau$
• SI-unit: Newton-metre $\mathrm{[N\cdot m]=[kg\cdot m^2/s^2]}$