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[in Japanese]

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[in Japanese]

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When humans ride a bicycle, they emit energy from their muscles to move forward. However, we are faced with a problem how the energy is succeedingly transmitted to the tip of the foot, petals, chains, axes of wheels, spokes, tires, and the ground. In fact, there have been many controversies as to “forces” which are introduced in those processes. In addition, the situation becomes complicated by the fact that “work” is expressed as the product of the force and the distance moved by the corresponding force. We have a desire to bring the concept of “rigid body” into the mechanical part in order to make the system idealized. However, such a naive concept makes the explanation rather unnatural. In brief, a paradox is induced by the extremely simple assumption that wheels and the ground touch at one point. In this note, wheels with spokes are regarded as a viscoelastic body to consider the contraction and the succeeding expansion. Therefore, we inevitably adopt multiple points (or surfaces) for the contact between wheels and the ground. As a result, we obtain the unified view for this mechanical prosses that the viscoelasticity of the muscles essentially helps the viscoelasticity of wheels with spokes.

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