# Inertia

## The tendency of an object to resist a change in its motion.

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Football Physics

### Football Physics

Credit: U.S. Navy photo by Mass Communication Specialist 1st Class Chad J. McNeeley

This quarterback has one goal: to run down the field as far and fast as he can. Defensive players on the other team will try to stop him by tackling him. Will the quarterback make it all way and score a touchdown? Who will win this gridiron battle? The answer depends on Newton’s first law of motion.

The Back Story

• Newton’s first law of motion is also called the law of inertia. It is one of many scientific laws.
• A scientific law is a statement describing what always happens under certain conditions in nature.
• Newton’s first law of motion states that an object’s motion will not change unless an unbalanced force acts on the object. An object at rest will stay at rest and an object in motion will keep moving in the same direction and at the same speed unless acted upon by an unbalanced force.
• The football player in the photo above is in motion. He will stay in motion unless players on the other team exert an unbalanced force against him.
• Watch this video to see how Newton’s first law controls what happens in a professional football game: http://www.nbclearn.com/nfl/cuecard/50884
• Credit: ?ick Perrone
Source: https://www.flickr.com/photos/nickperrone/8129436049

The receiver is tackled down by unbalanced forces from the opposing team [Figure2]

Can You Apply It?

1. What is inertia? Why is Newton’s first law of motion also called the law of inertia?
2. How is mass related to inertia? Why do you think football players are usually large in size?
3. A defensive football player on one team tackles the other team’s quarterback, who is running down the field. The quarterback is pushed to the ground by the defensive player. Apply Newton’s first law to explain what happened.
4. Apply Newton’s first law of motion to throwing a football.
5. What are some other examples of Newton’s first law in daily life?

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Color Highlighted Text Notes

2. [2]^ Credit: ?ick Perrone; Source: https://www.flickr.com/photos/nickperrone/8129436049; License: CC BY-NC 3.0

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