Spin and slice in tennis

Ball spin


Spin can be placed on any tennis shot. Spin can vary the depth, height, speed and bounce of a shot. There is top spin and slice (or back spin)

Top spin
Top spin makes the ball drop when it bounces. It spins in the same direction as the ball is hit.

To play it, hit through the ball from low to high. Make contact with the ball at about knee height and follow through to shoulder height. The faster the racquet head accelerates, the more topspin is produced.

Andy Roddick uses heavy top spin with every serve, because his serve being the fastest on record so far, he needs to ensure that the ball goes in.

The slice (or back spin)
Slice is made with control rather than power. It takes speed off the ball. Start with the racquet above the ball and hit down and through almost like you are cutting the ball. The bottom edge of the racquet strings should be in contact with the ball first. Slice is used for drop shots, low volleys and usual ground strokes. It can also be used as a counter shot to top spin and as an approach shot because it keeps the ball low. Pat Rafter used the slice a lot as an attacking shot, so he could get to the net for the next shot.

The physics of spin
Topspin needs gravity to work, so it can't be used on the Moon.
Actually, the ball spins fine, but spinning doesn't make it curve downward. The Moon has no air, and spinning balls only curve when they're flying through an atmosphere.

Physicists call this the Bernoulli Effect: Air pressure on one side of a spinning ball is higher than it is on the other side. High pressure pushes the ball toward low pressure--hence the curve. Swiss physicist Daniel Bernoulli wrote down the equations describing this curious phenomenon in the 18th century, setting the stage for Andy Roddick's devastating power game almost 300 years later.

The Bernoulli Effect is very important in sports. In baseball, it lets pitchers throw curveballs. In tennis and ping pong, it helps players ace their serves. In golf, it's responsible for the dreaded slice.