Putting It Together: Torque

Just like with some of our previous rotational variables, there are a couple of details worth remembering about torque.  First, when we talk about the torque exerted by a force, we always mean “the torque exerted by the force about a particular axis.”  Any torque calculation depends on the axis of rotation you are using.  Second, we are choosing to limit ourselves to thinking about rotational motion about a single axis.  We will make the same choice with torque.  Because we live in a world with three spatial dimensions, forces could generate torques around either the `x`, `y`, or `z` axes.  Because we will typically only deal with forces that act in the `xy` plane, we will only worry about torques about the `z` axis.  Three, though we often refer to the direction a torque will make an object rotate when thinking about its sign (typically clockwise or counter-clockwise), we should remember that torque is a vector.  As a result, the torque points along the axis of rotation and is more properly referred to as pointing into or out of the page.