| 摘要 |
A golf ball includes an inner layer, an outer layer, and a cavity therebetween. A fluid, such as a viscous damping fluid, is placed in the cavity. When the ball is struck, the inner and outer layers rotate independently of one another. Indicia are provided on the inner and outer layers. An examination of the relative position of the indicia before the ball is struck and after the ball is struck can yield data that indicate the shear force of the stroke.
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