Flying football physics

This exercise is a part of Educator Guide: Why Spiraling Footballs Sometimes Miss the Mark / View Guide

Directions for teachers: Ask students to read the online Science News article “Spiraling footballs wobble at one of two specific frequencies,” which describes how researchers figured out why spiraling footballs sometimes drift sideways, and answer the following questions. You may want to have students pair up to answer the first two questions as not all students are familiar with throwing a football. A version of the article, “Why spiraling footballs sometimes miss the mark,” appears in the September 10, 2022 issue of Science News.

1. Describe how footballs move through the air when they are thrown by football players.

A football is thrown so that it spins around its own axis as it travels through the air.

2. What does a wobbling football look like? What can happen to the football pass when a ball wobbles?

As a football spirals along its own axis when it’s traveling through the air, sometimes the nose of the ball sways from its direction of flight. That sway is considered a wobble. Wobbles can cause a football to drift sideways, away from its intended target.

3. What physical forces cause a football to wobble?

A football wobbles when its spinning momentum interacts with a twisting force.

4. How did scientists determine the rate of a football’s wobble? Make sure your answer includes the speed at which the ball traveled and its spiral and wobble rates and their appropriate units of measurement.

The scientists used computer simulations to find the wobble rates. Their football model traveled at about 27 meters per second, spiraled at a rate of about 600 rotations per minute and wobbled at a rate of either one or five times per second.

5. What did this new research find about football wobbles?

The wobble rates vary. A spiraling football can wobble fast or slow.

6. What makes a football’s wobble rate fast or slow? Explain.

How the ball is thrown determines the rate at which it wobbles. Faster wobbles occur when the player throwing the football moves in such a way that extra energy is applied to the ball.

7. How does wobble rate contribute to footballs drifting sideways? How far off course can a football drift due to wobbling?

A wobble rate of five times per second generates lift, which can cause the football to drift off course by several meters.

8. What other factors can contribute to a spiraling football getting off course?

Earth’s rotation and differences in air pressure.

9. How far off course can those factors cause the ball to drift? How does the amount of drift compare with that caused by wobbling?

Earth’s rotation and the effects of air pressure can cause the ball to drift by centimeters. That amount of drift is very small compared with the amount caused by wobbling — a centimeter is two orders of magnitude smaller than a meter.