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Static and Kinetic Friction Essays

1058 WordsOct 23rd, 20135 Pages

Static and Kinetic Friction


The amount of friction force between two surfaces in contact depends on the type of the surfaces in contact and the amount of compression between the surfaces. Static friction is the force that is acting against your force before the object begins to move. If you exert a small push on the box, the box will not move because static friction is directly opposite to the push. If you apply a greater force than the static friction force, the friction increases to match the magnitude of your push. There is a limit to the magnitude of static friction, so eventually you may be able to apply a force larger than the maximum static force, and the box will move. The maximum static friction force is…show more content…

Friction is the resisting force encountered when one tries to slide (static) or does slide (kinetic) one surface over another. This force acts parallel to the surfaces in contact. The force necessary to overcome friction depends on the nature of the materials in contact, their roughness or smoothness, and on the normal force. Experimentally, the force of friction is found to be directly proportional to the normal force. The constant of proportionality is called the coefficient of friction. The coefficient of friction is equal to the force of friction divided by the total normal force pressing the surfaces together. Thus, Ff = n, where Ff is the magnitude of the force of friction, n is the magnitude of the normal force, and is the coefficient of friction. A method of checking the above relationship is to have one of the surfaces in the form of a horizontal plane, with a pulley fastened at one end. The other surface belongs to a box to which is attached a cord passing over the pulley and carrying weights. These weights may be varied until the box moves uniformly when given a small push. The normal force magnitude between the two surfaces can be changed by placing weights in the box, and the relationship between the coefficient of friction, the force of friction, and the normal force can thus be tested. Another method of investigating

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The Physics of Football Essay

1222 Words5 Pages

The Physics of Football

There is no question that everything people do in their lives involves physics. This is true from the way we communicate to the way that we fight wars. In some cases the influence of the laws of physics on our world are extremely apparent, such as in sports. Basketball, hockey, baseball and even cricket involve physics. From the most basic motions players perform in the game, to different plays designed by coaches, physics touches it all. These appearances of physics in the games that we play are sometimes so subtle we don’t even notice them. In other cases however, the impact of physics can be heard across the stadium as Jerome “The Bus” Bettis barrels his way into the endzone. The influences of physics on…show more content…

For instance a wide receiver whose game depends greatly on being able to accelerate quickly will prefer to play on an artificial surface with less friction. When a player gets in the open field he may be capable of reaching his maximum momentum. When this player's momentum is suddenly changed either with a great tackle or one hell of a hit the laws of physics concerning collisions, both elastic and inelastic, come into play.

An elastic collision is a collision in which kinetic energy is conserved, such as when a running back is hit so hard by the opposing team’s linebacker on a lead-draw play up the middle that the ball is forced out of his arms. The fumbled ball then hits the turf and because of the elasticity of the collision it bounces back up. Unlike an elastic collision, an inelastic collision does not conserve the kinetic energy of the colliding objects (Kirkpatrick & Wheeler 134). An example of an inelastic collision might be when a player catches the ball (if he catches the ball) and the momentum of the ball is completely stopped. However it is important to realize in this study of physics that a completely inelastic collision is impossible to attain in the real world because the energy isn’t really lost it is just converted into different forms such as the sound the collision makes. So in a play where a ball carrier is in the open field, a would-be tackler would try to apply an impulse in an attempt to stop the other

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