Looking at just both angular velocity and torque, many other exhibit this same property. What is the purpose of and usefulness of having a direction that is in the Z-direction? (assuming that, in the case of torque, Force and moment length is x and y). I understand that since they are vector quantities they have to have both direction and magnitude, but I don't see the usefulness of the direction? I mean I can change the direction of torque depending if I choose counter-clockwise to be positive or negative?