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__**Physics**__ //
 * Newton's Law//Inertia
 * Aristotle-(4th century BC)
 * foremost scientist of the day
 * studied motion
 * Divided Motion into 2 categories
 * natural motion
 * violent motion
 * Natural motion- on Earth, this motion was straight up or straight down, as these were the directions of things falling (heavy) or rising light. Circular motion was only considere natural in the eavens, as Aristotle observed this type of motion with the planets, the moon, and the sun.
 * Violent motion- imposed motion, motion as the result of a "push" or a "pull"; it had an external cause


 * Copernicus-(1473-1543)
 * He reasoned that the simplest way to interpret astronomical observations was to assume that the Earth and the other planets move around the Sun
 * He did most of his work in secret, to avoid persecution
 * In his last day he sent his ideas to be printed and recieved the first copy of his work on the day of his death
 * Galileo-(1564-1642)
 * Gave his support for Copernicus' idea, and was put on trial and placed on house arrest for it
 * One of his greatest contributions to physics was breaking the idea that a force was required to keep an object moving
 * All of his work was done before mechanical clocks were invented, so he timed some of his experiments with his own pulse, or with dripping water
 * Force- any push or pull
 * Friction- force that acts between materials that are touching as they move past each other
 * Friction is caused by the irregularities in the surfaces of objects that are touching
 * Even very smooth surfaces mave microscopic irregularities that obstruct motion
 * Galileo argued that only when friction is present is a force needed to keep an object moving
 * Galileo- started that the tendency of a moving object is to keep movng and without friction, it will; contrary to Aristotle's notion that the natura state of objects is to be at rest
 * This property of an object to resist changes to its motion is called "Inertia"
 * Isaac Newton- (Born on christmas day, same year that Galileo died)
 * By age 24, developed his laws of motion
 * First Law of motion- Every object continues in a state of rest, or in motion at a constant speed in a straight line, unless acted on by an outsode force
 * In other words, things tend to keep doing what they are doing
 * First part of the 1st law is ratehr apparent, objects tend to stay at rest- objects do not sppontaneously move without forces applied to them
 * Second pat of the 1st law is not as apparent, objects in motion tend to stay in motion
 * Ex. is taking a hockey puck and sliding it across pavement, then sliding it across ice, and if you had an air table (air hockey) long enough, it would go even further
 * Mass- a measure of inertia
 * Ex. if you kick an empty can, it wll move quite easily If you kick a full can of soda, it will move, but not as far// If you kicked a can filled with cement it might hurt, and will not go very far at all
 * So the more mass an object has, the more it resists change, or the greater its **Inertia**, and the more force it takes to cange its state
 * Mass is not weight, although it is often confused with weight
 * Mass is a measure of the amount of materil in an object, the number and kinds of atoms that compose it
 * Weight is the measure of gravity's effect on the same object
 * When astronaunts go into space, their molecules do not change, so their mass remains the same, while their weight does not
 * Mass is inertia
 * The amount of material in a particular rock is the same whether the stone is on Earth, the moon, Mars, or in a deep space, its mass stays the same
 * The amount of force to shake the rock back and forth with a rhythm would be the same in all the locations
 * the rock's inertia is the same regaurdless of its weight (weightless does not equal zero inertia)
 * Astronuts working on the space station in zero gravity can push on th station without moving it, as its inertia is still great due to its great mass, while still having zero weight
 * Mass- quantity of matter in an object
 * Weight- force of gravity on an object
 * While these two things are not the same, in a given location, they are proportional
 * Things with more mass, will have more weight in a gravity field
 * In the USA we describe matter in terms of weight, in pounds
 * In the rest of the world, they use the metric standard unit of mass, the kilogram
 * The standard unit of force is called the NEWTON, Named after Isaac Newton
 * 1 kg= 10 n
 * 16th century- Copernicus announced the idea of a moving Earth, meaning that it was moving in a space around the sun
 * This idea was greeted with much debate
 * The argument went like this
 * If a bird were sitting in a tree and the bird spotted a worm on the ground, if the bird jumps off the tree and drops down vertically to catch it. If the earth is moving t the rate that Copernicus suggests, (about 30 km/ sec) then the worm and the ground it is on will have moved 30 km away before the bird got to the ground. The fact that the birds drop from the tree and catch worms proved that the Earth could not be moving, right?
 * Here is why not, not just the Earth is moving at 30 km/ sec, but everything on it as well
 * No different than when you are in a car and you pick something up and drop it inside the moving vehicle, and it dosn't fly to the rear of the car
 * Newton's second law of motion
 * Wen forces on an object are balanced, no acceleration hhappens, no change in velocity or position
 * Objects that are stationary have only balanced force ( gravity vs. resisting forces)
 * When net (sum of all forces) force is not zero, the object accelerates
 * in Physics - acceleration= a change in motion, either speed, direction, or both
 * Can be slowing down or speeding up
 * To increase the acceleration on an object, you must increase the net force
 * acceleration is directly proportional to net force, if you double one, you double the other
 * Mass Resists Acceleration
 * an increase in mass results in a decrease in acceleration ( if net force stays same)
 * For a given force, the acceleration produced is inversely proportional to the mass
 * Twice the mass= one half the acceleration
 * 3 times the mass= one third the acceleration
 * Newton's second law= states that the acclereation produced by a net force on an object is directly proportional to the magnitude of the net force, is in the same direction as the net force, and is inversely proportional to the mass of the object
 * Acceleration= Net force/ Mass
 * Applying force- pressure
 * If you balance a book on a table, the force of the book on the table is the same no matter whether it is laid flat or stood on its end
 * On a scale yu weigh the same standing on one foot or on both or sitting
 * But if you balance the book on your hand on its edge, then lay it flat on your hand, you will notice diffrences in the way the book presses on the hand
 * For a constant force, an increase in the area of contact will result in a decrease in the pressure
 * This principle is how laying on a bed of nails work. If there were only a ew nails, you would not want to lay on it, but with hundreds of them, the pressue per area is decreased. and the nails will not uncture the skin
 * free fall- when a falling object encounters no air resistance
 * Galileo showed that fallimg objects accelerate equally, regaurdless of masses
 * While this is strictly true with no air resistance, this is approximimatily true when air resistance is very small compared to the mass of the objects
 * ex.- a 10kg. stone and a 1kg. stone are dropped at the same time from the same height
 * The stones will accelerate at close to the same rate and will hit at close to the same time