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 Subject: Newton's Inertia. Category: Science Asked by: trunks1054-ga List Price: \$3.50 Posted: 03 Dec 2002 17:56 PST Expires: 02 Jan 2003 17:56 PST Question ID: 118777
 `I want information about Newton's discovery of Inertia.` Request for Question Clarification by googlenut-ga on 03 Dec 2002 19:41 PST ```Hello trunks1054-ga. Are you looking for a technical description of Newton's Law of Inertia or historical information about how he came to dicover inertia or some combination of the two? I have come up with some information, but I want to make sure it's what you are looking for. Googlenut```
 ```Hello trunks1054-ga. I decided that I could answer your question without clarification because any answer would have to include a technical discussion as well as an historical one. Actually, Newton did not actually discover inertia. It was Galileo who first introduced the concept of inertia. I found a paper written by a group of students at Penn State University which summarizes it very well (http://class.phys.psu.edu/p001fa02/projects/Project1/CulturalProjects/41Galileo%20and%20Inertia.doc): “Galileo formally introduced the concept of inertia as a physical truth. Inertia, according to Galileo, is the property which all matter possesses that resists a change in motion. It is inertia that keeps an object moving at constant velocity and resisting any changes to that velocity unless acted upon by an outside force. Thus if a ball is started rolling, it will continue to roll at the same speed and in the same direction of the original force unless an outside agent acts upon it” They go on to say: “Although Galileo was credited with noticing the phenomenon, it was Newton who published and named the concept officially. Galileo’s idea allowed Newton to come up with his first law of motion, which basically states that an object will stay at rest or in uniform motion unless an outside force acts upon it. This clearly spurs directly from Galileo’s concept of inertia.” The Law of Inertia is the first of Newton’s three Laws of Motion (the second and third being the laws of “Force” and “Action and Reaction”, respectively). Newton’s First Law of Motion, the “Law of Inertia” is commonly stated at follows (ref: Inteliquest Media Corporation, http://www.4iq.com/newtontxt.html): “If a body is at rest or moving at a constant speed in a straight line, it will remain at rest or keep moving in a straight line at constant speed unless it's acted upon by a force.” Newton’s Law of Inertia explains why, if a person is sitting in a moving car, and the car is caused to suddenly stop by hitting something, the person will continue to move forward until they are held back by the seat belt, or until they hit the steering wheel or windshield if they are not wearing a seatbelt. It also explains why a person sitting in a car moving in a straight line, will be forced to lean when the car makes a sharp turn. The person’s body will tend to continue in the direction of the original motion until the friction of the person on the seat forces them to also turn. A question may be, “what is really the difference between Galileo’s Law of Inertia and Newton Law of Inertia. In a lecture titled “How Newton Built on Galileo’s Ideas”, Michael Fowler, of the University of Virginia Physics Department (http://www.phys.virginia.edu/classes/109N/lectures/newtongl.html) states: “Galileo's analysis of projectile motion was based on two concepts: 1. Naturally accelerated motion, describing the vertical component of motion, in which the body picks up speed at a uniform rate. 2. Natural horizontal motion, which is motion at a steady speed in a straight line, and happens to a ball rolling across a smooth table, for example, when frictional forces from surface or air can be ignored.” Fowler goes on to say: “Newton's major breakthrough was to show that these two different kinds of motion can be thought of as different aspects of the same thing. He did this by introducing the idea of motion being affected by a force, then expressing this idea in a quantitative way. Galileo, of course, had been well aware that motion is affected by external forces. Indeed, his definition of natural horizontal motion explicitly states that it applies to the situation where such forces can be neglected. He knew that friction would ultimately slow the ball down, and--very important--a force pushing it from behind would cause it to accelerate. What he didn't say, though, and Newton did, was that just as a force would cause acceleration in horizontal motion, the natural acceleration actually observed in vertical motion must be the result of a vertical force on the body, without which the natural vertical motion would also be at a constant speed, just like natural horizontal motion. This vertical force is of course just the force of gravity.” There is a great deal of information on the Internet about Galileo and Newton’s Law of Inertia. In addition to those websites I referenced above, a few good references are listed below: The University of Tennessee Knoxville, “Galileo: the Telescope & the Laws of Dynamics” http://csep10.phys.utk.edu/astr161/lect/history/galileo.html Zona Land, “Galileo and Inertia” http://id.mind.net/~zona/mstm/physics/mechanics/forces/galileo/galileoInertia.html A GUIDE TO PHYSICS, “Physics Timeline” http://www.aguidetophysics.com/Timeline.htm Workforce Silicon Valley Engineering/Technology Curriculum “Sir Isaac Newton Biography” http://engineering-ed.org/Aerospace/Resources/Sir%20Isaac%20Newton%20Biography.doc Mark Alford, Massachusetts Institute of Technology, “Isaac Newton: the first physicist” http://www-ctp.mit.edu/~alford/newton.html Newton's Laws of Motion, Eastern Illinois University http://oldsci.eiu.edu/physics/DDavis/1350/05Laws/ToC.html I hope you have found this information helpful. Please request clarification if you would like additional information. 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