Forces

On this page please define the force, give the equation and explain the variables.

Newton's First law of motion Newton's Second law of motion Newton's Third law of motion Horse / Cart Paradox "There once was an intelligent horse by the name of Einstien. One day while running around with his cart Enistien stop by the local high school. One of the student explained to Einstein Newton's three laws of motion. After the student left Einstein sat there in front of the school the entire day, until another student asked the Einstein what he doing. Einstein responded "I can't move the Cart, because a net force is needed to change the motion of the cart but every time I apply a force an equal and opposite force is applied back, so it's pointless to try". How can Einstein pull the cart and not violate Newton's laws?

Weight / Force of Gravity  **Static Friction **: Static friction is a force between two objects that are not moving relative to each other. The coefficient of static friction is normally μs and normally it is greater than kinetic friction. Static friction acts between surfaces at rest with respect to each other. The value of static friction varies between zero and the smallest force needed to start motion. This smallest force required to start motion, or to overcome static friction, is always greater than the force required to continue the motion, or to overcome kinetic friction. -Ralph Stage This illustretes what happens when you don't overcome static friction: http://www.youtube.com/watch?v=fXWF08Ws73s&feature=related


 * Kinetic Friction**: Kinetic (or dynamic) friction occurs when two objects are moving relative to each other and rub together (like a sled on the snow) . If you try to slide two objects past each other, a small amount of force will result in no motion and if you apply a little more force, the object "breaks free" and slides, although you still need to apply force to keep the object sliding. This is kinetic friction. You do not need to apply quite as much force to keep the iobject sliding as you needed to originally break free of static friction. -Ralph Stage. Stupid people + Kinetic Friction video: http://www.youtube.com/watch?v=AAvRrNIn4V4&feature=related or http://www.youtube.com/watch?v=QA-9i6mD3N0&feature=related

 Normal :  Tension: Tension is the magnitude of the pulling force given by an object similar as a string, chain, etc. Tension is always parrallel to the object and is usually measured in kgm/s2. For systems of objects held by strings, there are two basic possibilities: Either acceleration is zero and the system is therefore in equilibrium or there is acceleration and therefore a net force is present. Tension is present in instruments such as guitars, violins, and cellos on the strings; they each have a different magnitude of tension so the instruments each have a different pitch.

Here is a perfect example of tension. -KEVIN

Spring :  Air Resistance: