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# The Physics of Football

Passing the Footbal
by

## Binyam Belay

on 20 May 2011

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#### Transcript of The Physics of Football

The Physics of Football By: Binyam Belay 4th period By: Yours very truly,
Binyam Belay Even though some people think that football is just who runs the fastest or who is the strongest, many physics concepts are in football. Here are some of the many physics concepts that are involved with throwing a football: Since football in general is such a large topic with a lot of physics concepts, I will only talk about the physics behind the passing aspect Vectors
Projectile Motion
Law of Inertia
The Kinetic Chain
Kinetic/Potential Energy
Newton's 2nd Law
Rotational Motion
Torque Vectors So when you watch football, it's easy to notice that you the quarterback has to throw the ball with a certain force in order to get the football over a certain distance. Well, you can't simply describe the action with one word. This is why we use vectors to correctly describe the force that acts on the football All vectors have a scalar, a quantity that is described by a magnitude, or an amount. In this case, we have a velocity vector, where the ball travels with a speed and a direction Other scalars include distance, height, and angles Projectile motion So what happens when the ball begins to fly in the air, you say? So, in physics, we describe this motion as motion of the center of mass of an object, in this case, the football, moves through space with a constant acceleration of -9.8 meter/second/second. So after the quarterback releases the football, it follows the trajectory, or path, of a parabola. A parabola looks closely similar to a half oval. The projectile motion is also called 2-D motion because both horizontal and vertical motion occurs at the same time. Which is simple to do because the components are independent of each other. Once you seperate the two components, it isn't as hard to solve the motion problems. As the football travels along it's trajectory, the projectile moves the same velocity that the quarterback released the ball. The vertical component on the other hand because the vertical distance and celocity depends on the starting speed, angle at which it is thrown, and the downward acceleration due to gravity, which comes to be a -9.8 m/s/s This type of vertical motion that is only affected by the force of gravity is described as free fall So the horizontal distance the football travels can be calcuated by multiplying the horizontal speed and the amount of time the ball is in the air. Lastly, many quarterbacks have to make quick decisions in their head to determine what angle to throw the football, depending on where the target is The Law of Inertia One of the most brilliant scientists in history, Sir Isaac Newton developed a a series of fundamental laws that had to do with objects in motion, and th relationship between the object's mass, the forces, and the displacement of those objects His first and some say his most important one stated that objects continue with the motion that they already have unless acted upon by other forces. ANd ifthere are no forces, then the object will stay at rest. This is called Newton's 1st law of motion, or The Law of Inertia. So let's put this in football terms, shall we? For example, when the quarterback sets the ball at the line of scrimmage, the football is at rest until the center hike sit to the quarterback. Once the quarterback has been hiked the ball, he takes his drop depending on how far he must throw the ball, and launches the football which is now in motion, and will stay in motion until the reciever catches it, or until gravity brings it down. Air resistance is also usually involved in real world situations, like NFL games. The Kinetic Chain So where does the QB get all of this energy from? Now I know you're assuming that this is something totally oh so very complicated. But in truth, we use it every day, just like all of the other physics concepts. In fact, it's exaclty what it sounds like; it's a chain of energy where energy begins to add up until it is released. At the beginning of the play, the quarterback takes his drop, not only to see where the defense is, but to also gain energy. While he is shuffling back, he begins to conserve energy in his legs, which is the starting point of the chain. After he plants his feet, the kinetic energy becomes energy in place, or potential energy. But not for long.... As the QB begins his throwing motion, the energy that was conserved in his legs beings to move to his hips where he gains more kinetic energy After this occurs, the kinetic energy moves to the multiple levers in his arm, where he again, gains more energy So at the last part of the chain, all of the energy moves into his wrist and the football, and the QB releases the ball. Newton's 2nd Law Although many people forget about the law, we unconsciously act upon it every day. This law basically says that both the mass and the acceleration of an object are directly proportional to it's force. (F=ma) .... which just means that you need to push or pull with a certain force for an object to move, depending on it's mass and how fast you want it to move. Now that you understand the law, you find out that you think about it every day. So let's say that.... Rotational Motion So now we get to talk about one of the coolest things about throwing the football; the spiral. - rotation around a fixed axis When the QB is about to release the ball out of his hand, he rolls his index finger aong the football's axis of rotation. You can find the axis of rotation by using the concept of the right- hand rule with the football After the ball is released from his hand, the projectile begins to roll along it's axis of rotation, creating a pocket of air around it, which minimizes the amount of drag on the ball So with all of this in mind, how accurate is the NFL Quarterback? I'll let SportScience take it from here And that my fellow physicists, is the physics of throwing a football The Physics of Football: The Aerial Aspect
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