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| This is an illustration
of rolling motion. Place the cylinder on the table with the white
dot at the point of contact. Place the meter stick on the cylinder
so that the front edge of the stick is lined up with the top of the cylinder.
Place a fiducial object (eraser, piece of chalk, etc.) to mark the
position of the initial point of contact. Call this point A.
Roll the cylinder on the tabletop making sure that the meter stick rolls on the cylinder without slipping until the white dot makes one complete revolution. Place fiducial marks at new point of contact (Point B) and new horizontal position of the meter stick's leading end (Point C). Point out that in the same time that the center of the cylinder moved from Point A to Point B, the leading edge of the stick moved twice the distance from Point A to Point C. Conclude that the top of the cylinder moves at twice the speed of the center while the point of contact is instantaneously at rest. (PIRA 1Q20.30) |