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Backspin - How does it Work?

Backspin Force Direction
(c) 2006 Greg Letts, licensed to About.com, Inc.
With backspin, the bottom of the ball is moving in the same direction that the ball is travelling. The force exerted on the ball by its spin will be generally upwards (again, assuming the ball has been hit almost horizontally). This upward force works in the opposite direction to gravity, causing the ball to drop more slowly.
Since a table tennis ball is light and easily slowed by air, a heavy backspin stroke performed from several feet from the table will often slow down it's forward speed quite noticeably over the opponent's side of the table, then slowly fall onto the playing surface. This 'stop and drop' effect is used by defenders when playing against topspin attacks.
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