Physics of Sport - Football
NEWTON'S FIRST LAW (LAW OF INERTIA)
Newton’s first law states that an object in motion tends to stay in motion, and an object at rest tends to stay at rest, unless acted upon by an unbalanced force. In easier words, when an object is not moving, it's not going to move unless some other object or force acts upon it. This law occurs when a football is being thrown and, a defensive player. The object in motion is the offensive player. Once he has the ball, he will run at a constant velocity. The unstable force is the defensive player. The defensive player wants to stop the offensive player, and in this case, that would mean a tackle. As soon as the defensive player tackles the offensive player, the offensive player’s velocity changes dramatically. This interaction demonstrates Newton's first law. I know that this law occurs when throwing a football because we see the ball start to move as soon as the thrower releases it from his hand, meaning that as soon as an unbalanced force is applied, the ball changes from resting to moving.
Law of Inertia shown in a football throw.
Law of Inertia shown in a football tackle.
FREE BODY DIAGRAMS
In the first FBD it shows that there is and Applied Force because the football is being thrown by the thrower, Force of Gravity and, static friction. There is minimal force pushing back horizontally against the applied force, which is why the football accelerates forward. There is a force pushing down vertically, but the force applied from the thrower is much greater than the force of gravity, the football is able to overcome it and accelerate the ball upwards.
In the second FBD While the football is in the air, the only force acting on it is the force of gravity, because air resistance was minimal. Since nothing else is acting on the ball, no other forces can be applied.
The third FBD repersents when the football has traveled through the air to my partner. Once my partner catches the football there are three different forces acting on it. The first is the force of gravity, which is pushing it downwards toward the ground but, since it is no longer moving downward, we know that there must be an equal force pushing back against gravity and causing it to remain at the same height which is the normal force. The third force acting on the football is the force of kinetic friction. Friction is caused by my partner catching the ball. Force of friction causes the ball to slow down. Kinetic Friction opposes motion of a moving object.
Free Body Diagrams at the three different stages when the ball was thrown.
Denver Broncos quaterback Peyton Manning.
