WHY? The mechanism by which the forces change magnitude and direction is not known. However, one can theorize that the stitches play a key role. The stitches will most likely cause the boundary layer to trip too a turbulent state. Other dirty tricks employed by pitchers involve scuffing the surface and/or polishing the surface. Just as a rough surface promotes turbulent and, therefore, attached flow, a polished surface will maintain laminar flow and hence separated flow. By roughening one side and polishing another, the effects of various pitches will be exaggerated. So, in reality, a pitcher is not just a ball player, but an amateur aerodynamicist as well. ASSESSMENT: Can the student communicate what they observed?

Student is able to communicate how the surface of a knuckleball goes from a laminar flow to a turbulent flow and visa versa because of the stitches on the baseball and also scuffing the surface and/or polishing the surface of the ball. Student is able to communicate most of the reasons how the surface of a knuckleball goes from a laminar flow to a turbulent flow and visa versa because of the stitches on the baseball and also scuffing the surface and/or polishing the surface of the ball. Student is able to communicate some of the reasons how the surface of a knuckleball goes from a laminar flow to a turbulent flow and visa versa because of the stitches on the baseball and also scuffing the surface and/or polishing the surface of the ball. Student is able to communicate one of the reasons how the surface of a knuckleball goes from a laminar flow to a turbulent flow and visa versa because of the stitches on the baseball and also scuffing the surface and/or polishing the surface of the ball.

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Last modified: Tue Aug 26 15:00:09 PDT 1997

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