I recently answered this question: Laminar Versus Turbulent Flow and it caused me to think of the following situation.

Given that an (American) football weighs between Football 400 to 430 grams, and a (FIFA Rules) soccer ball is in the same weight range, 410 to 450 grams, which will travel further, when thrown under the same conditions?

I am assuming both are the same weight, say 420 grams, and both are fired into still air at the same angle, say 45 degrees, by a machine that imparts the same initial velocity to both of them. Also no spin is involved, although it would be interesting to see, if the soccer ball was allowed to spin, would that reduce drag, by reason of the planar-like surfaces it is composed of, and the regular ridges between the panels?

I am assuming no spin of any kind and the same "flight path" but any answers that incorporate more realistic situations will be welcomed. It's the difference in drag that I was initially interested in, but any answer that applies reality to the problem is appreciated.

enter image description here

Please ignore the relative sizes shown in the picture, as these are chosen at random.

In professional play the football has a long axis of 28 cm , a long circumference of 71 cm, and a short circumference of 53 cm. The soccer ball has a diameter of 22 cm and a circumference of 70 cm.

My guess would be the football, rather than the soccer ball, because of it's shape, and if so, can any estimate be made of the extra distance?

I do realise that this is a "novelty" type question, compared to the majority of questions received here, but I do think that there may be some interesting fluid dynamics related physics involved.

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    $\begingroup$ PUtting spin on either ball can improve the aerodynamics, i.e. reduce the forward drag. But in typical Physics 101 fashion, "assume perfectly smooth surfaces and uniform density" , and the fact that the egg-ball presents less forward surface suggests it'll have far less drag. $\endgroup$ – Carl Witthoft Sep 6 '15 at 12:23
  • $\begingroup$ @CarlWitthoft My picture is misleading, suggesting that the soccer ball is much bigger, but I will try to get dimensions for the post. I would be suprised if the football was not way ahead, thanks. $\endgroup$ – user81619 Sep 6 '15 at 12:29
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    $\begingroup$ @AcidJazz But is the football trajectory stable without rotation? $\endgroup$ – Bernhard Sep 6 '15 at 12:34
  • $\begingroup$ @Bernhard I am assuming no spin of any kind and the same "flight path" but I will modify the post to reflect your comment thanks. $\endgroup$ – user81619 Sep 6 '15 at 12:41

The drag force on an American football is in the range of a coefficient of .05 to .06. If the football is spinning the drag is slightly less.

The drag on a FIFA soccer ball is a coefficient of .25.

The football should travel further. The diameter of an NFL football is about 17.3 centimeters. The diameter of a FIFA soccer ball is roughly 22 centimeters. The greater cross sectional area of the soccer ball creates a thicker wake and more drag, as Sebastian Riese points out in his comment.

The chief difference between the balls, which produces less drag on the NFL football, is the shape. The NFL football's wake is significantly thinner than the soccer ball's, to a great extent because of the shape of the ball. The hulls of ships, for example, are designed like a football's shape below the water line toward the stern in order to allow a more laminar flow as the boundary layer separates from the back of the hull. Laminar flow creates a thinner wake which produces less turbulent viscous drag.

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    $\begingroup$ Plus the area (perpendicular to the flow) of the latter is larger. $\endgroup$ – Sebastian Riese Sep 6 '15 at 12:44

Hmmm - the above answers assume that the american football (I'm a Brit) or rugby ball (they are similar shapes) does not start to tumble in flight. Every rugby player knows to throw a spin pass - ie to impart spin onto to the ball around the long axis while throwing the ball in the direction of the long axis to ensure that the pass stays true - basically emulating the function of rifling in artillery. From what I've seen of American football quarter back play - their passes are thrown similarly - albeit one handed.

Comparing the distance of punts in rugby and association football leads me to wonder whether the football flies further - because of the impact of tumbling but the evidence is inconclusive. There have been soccer goals scored by goal keepers from punts - the first bounce ends up close to the opposition penalty area - that kind of distance for a goalkeeper is relatively commonplace and is about 70m. In rugby, a similar distance is from home 22m to opposition 22m line - a rugby player kicking from inside his 22m line to touch in the opposition 22m area would be a huge asset - and is uncommon from my experience. The distance here might be ~70m (60m from 22 to 22 + an addition for the crossfield element of the kick. The nature of the game would be that such a kick would be aimed to go out of play between 22m and goal. The rules of the game make it less likely that the kick be from outside the 22m line. Rugby players regularly place kick from inside their own half to score "penalties" ~60m. Unlike gridiron - rugby and soccer pitchs do not have defined lengths ~100m within a margin is the rule for both sports.

I am sure some statto will have distances for the longest punts in gridiron - I dont.

In conclusion - long kicks in both Soccer and Rugby are ~70m - imparted by the same implement, the human foot. It would be interesting to see some more conclusive evidence - but that would take experimentation.

  • $\begingroup$ The longest field goals in NFL history were 60 - 63 yards. If you add in another 10 feet after the ball clears the crossbar, the total distance is about 60 meters. Compared to these distances, NFL field goals must go through a relatively narrow pair of uprights. This fact, plus various other rules, discourage trying very long field goals. By the way, the longest NFL field goal was kicked using half a human foot. $\endgroup$ – Jasper Nov 11 '16 at 4:45