Why does a rugby ball's flatter ends make it travel differently (through the air) than a football, when they are almost the same otherwise?

A football and a rugby ball are quite similar in shape and size. Both balls are oval and are 11 inches long. The difference between the two is the shape balls' ends. The football has ends that come to a point--while the rugby ball has flatter ends. The ends of these balls make a significant difference in how each moves through the air.

The football has a more streamlined design and consequently has less drag--allowing the ball to move more easily through the air. The rugby ball, with its flat ends, has more drag as it is passed from player to player through the air. There is more drag on a rugby ball traveling at the same velocity as football. The rugby ball is also more prone to tumbling end over end--an extremely inefficient way of traveling.

The differences in the way the two sports are played take advantage of the design of each particular ball. The optimal way to pass a football is in an overhand motion that creates a "spiral"--this gyroscopic motion makes the ball more stable in flight. The stability of the football's flight allows players to execute plays that require pinpoint passes and precision timing. It also allows some players to throw the ball 70 yards or more!

In rugby, the passes are generally shorter and are executed with an underhand motion. The ball retains some stability in flight on short passes, but tumbles end over end in longer passes or kicks.