# A Better Golf Game

## Physicists, Mechanical Engineers Design Better Ball for Amateurs

January 1, 2005

Researchers have designed a golf ball that tends to fly straighter even when a putter unintentionally "slices" it which ordinarily causes it to curve to one side. The new ball has a hollow, metal core that shifts the ball's mass -- or weight -- to the outside. This helps the ball spin less and fly straighter as it sails through the air.

## What makes a golf ball fly?

The aerodynamics of a golf ball involves two pairs of opposing forces: lift and weight (the pull of gravity), and thrust and drag.

Hitting a golf ball creates a forward thrust. It also creates a rapid back spin on the ball as it travels. This forces the air flow downward and produces lift. Lift occurs whenever the air pressure beneath an object, like an airplane's wing, is greater than the air pressure above it.

But a golf ball can't travel in the air forever: the force of lift is countered by the equal and opposite force of drag -- the result of air friction on the ball's surface -- and the pull of gravity (since the object has weight). Eventually these forces become greater than the lift and thrust, and the golf ball falls to the ground.

There are other factors that contribute to how far a golf ball can travel through the air. Balls with a harder core travel further because they don't buckle as much when hit by the golf club, so more energy is transferred from the swing to the ball. The dimples are also important when it comes to keeping the ball in the air longer. Dimples allow air to flow over the ball's surface more easily, with less friction, and therefore less drag.

A golfer can improve the distance the ball travels by using correct technique. At the back of the swing, a golfer should reach as far back as possible for the greatest range of motion, while keeping his rotating torso centered over his right leg. As the golfer swings, his body creates a torque (twisting force) on the club as it moves forward through the swing, gaining energy as it accelerates. The more tightly he controls his motion, the less energy is wasted, and the more energy there is available to transfer to the golf ball upon impact. When the club hits the ball, the golfer should drive through the swing to ensure maximum transfer of energy.

The American Physical Society contributed to the information in the TV portion of this report.

## Did you know?...

The earliest golf balls were spherical leather pouches filled with goose feathers, called "featheries."

Conduct your own experiment by removing the dimples on a golf ball using sandpaper. Apply several coats of white spray lacquer to make it very smooth. Then head out to the practice tee and compare how far you can hit the smooth ball compared to a regular dimpled ball. You'll find the dimpled ball will travel farther.