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Rolling Ruler
A rolling ruler is a ruler that contains a cylinder (geometry), cylinder much like a rolling pin inside, thereby enabling it to "roll" along a sheet of paper or other surface where it is being used. A rolling ruler can draw straight, parallel lines, and also has other instruments included, enabling it to do the jobs of a protractor and compass (drafting), compass. The modern rolling ruler, with protractor, pivot pin and multiple pin holes serving as fixed length compasses has been patented in the US in 1991 by Wei Wang. References [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rolling Parallel Ruler
Rolling is a Motion (physics)#Types of motion, type of motion that combines rotation (commonly, of an Axial symmetry, axially symmetric object) and Translation (geometry), translation of that object with respect to a surface (either one or the other moves), such that, if ideal conditions exist, the two are in contact with each other without sliding (motion), sliding. Rolling where there is no sliding is referred to as ''pure rolling''. By definition, there is no sliding when there is a frame of reference in which all points of contact on the rolling object have the same velocity as their counterparts on the surface on which the object rolls; in particular, for a frame of reference in which the rolling plane is at rest (see animation), the instantaneous velocity of all the points of contact (e.g., a generating line segment of a cylinder) of the rolling object is zero. In practice, due to small deformations near the contact area, some sliding and energy dissipation occurs. Neverthe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
