Editing Screw theory (section)

=== Wrench ===
The force and torque vectors that arise in applying Newton's laws to a rigid body can be assembled into a screw called a '''wrench'''.  A force has a point of application and a line of action, therefore it defines the [[Plücker coordinates]] of a line in space and has zero pitch.  A torque, on the other hand, is a pure moment that is not bound to a line in space and is an infinite pitch screw.  The ratio of these two magnitudes defines the pitch of the screw.