| 摘要 |
Indicia on the surface of a football (for the American variety of the sport) are provided to provide visual means for assessing the spin speed of the football when thrown in a desired manner. In one embodiment, the indicia comprise a circumferential indicator ring consisting of a plurality of alternatingly-colored segments, the indicator ring being aligned with the desired direction of spin of the football. The segments are preferably selected to be of contrasting colors, and the width of the segments is selected such that the indicator ring appears to an observer to be a single, mixed color provided the football is spinning about its axis at at least a predetermined frequency. In another embodiment, the indicia comprise two or more circumferential indicator rings at least one of which comprising a plurality of alternatingly-colored segments. The respective segment widths on one or more rings may be selected such that the mixed color of one ring, and hence the spin speed of the football, can be assessed relative to the color or mixed color of another ring.
|
