Avoiding sliding friction — a major sinkhole of applied force for motion — is accomplished through rolling. A: Ironically, with increased friction at the rolling contact surface. Wheels need ...

In this case, a fine structure, caused by intramolecular motion induced by the tip ... to the next during the manipulation. Figure 3: Rolling and hopping of wheel-dimers by lateral manipulation ...

And here's what they found. Under normal rolling conditions, the forward motion of the suitcase is perpendicular to the wheels' axis of rotation. All good. But when you hit a bump or jerk the ...