Absolute Motion, Rolling Disk

Position of Point O

Point O moves only in the x-direction. The horizontal distance traveled by O is related to the angular rotation, q. It is equal to the arc length of the edge of the disk which comes in contact with the floor.

rO = (r q) i

Position of Point A relative to O

This can also be expressed in terms of q.

rA/O = (r sinq) i + (r cosq) j

Position of Point A

rA = rO + rA/O

rA = (r q + r sinq) i + (r cosq) j

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