Choice of positive direction of coordinate axis in the plane-parallel motion of rigid body
Plane-parallel motion,as an important type of rigid body motion,is an important teaching content in the course of physics mechanics and theoretical mechanics.Because plane-parallel motion involves both translational and fixed axis rotation,between which there is often a certain constraint relationship,it is also a difficult teaching point.The main difficulty is that beginners often miss the possible negative sign in the constraint relationship because they specify the positive direction of coordinate axis arbitrarily.According to the force analysis,after assuming the trend of the plane-parallel motion of the rigid body,selecting the positive direction of the coordinate axis appropriately can avoid the negative sign in the constraint equation,so that students can analyze the rigid body motion problem more quickly and accurately.
rigid bodyplane-parallel motionpositive direction of coordinate axisconstraint equation