Topspin

In ball sports, topspin is a property of a ball that rotates forwards as it is moving. Topspin on a ball propelled through the air imparts a downward force that causes the ball to drop, due to its interaction with the air (see Magnus effect). Topspin is the opposite of backspin.

In baseball, the curveball, a type of pitch which usually has downward movement, is thrown in such a way as to put topspin on the ball. Its close relatives are the slider and the slurve. The "curve" of the ball varies from pitcher to pitcher.

In snooker, pocket billiards and billiards, players use topspin to keep the cue ball moving, including after it hits other balls. They get top spin by hitting the cue against the top of the ball.

In cricket, a top-spinner is a type of delivery bowled by a cricketer bowling either wrist spin or finger spin. In either case, the bowler imparts the ball with top spin by twisting it with his or her fingers prior to delivery. In both cases, the topspinner is the halfway house between the stock delivery and the wrong'un - in the wrist spinner's case his googly, and in the finger spinner's case his doosra.

A topspinning cricket ball behaves similarly to top spin shots in tennis or table tennis. The forward spinning motion impedes air travelling over the ball, but assists air travelling underneath. The difference in air pressure above and underneath the ball (described as the Magnus effect) acts as a downward force, meaning that the ball falls earlier and faster than normal.

In cricketing terms, this means that the ball drops shorter, falls faster and bounces higher than might otherwise be anticipated by the batsman. These properties are summed up in cricketing terms as a "looping" or "loopy" delivery. Also, the ball travels straight on, as compared to a wrist spin or finger spin stock delivery that breaks to the left or right on impact. A batsman may easily be deceived by the ball, particularly given that the action is quite similar to the stock delivery.

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