AP1200_Ch1_Mechanics-3Dynamics-2007

AP1200_Ch1_Mechanics-3Dynamics-2007 - AP1200 1. Mechanics...

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1 AP1200 – 1. Mechanics Concepts AP1200 – 1. Mechanics Concepts 1.3 Dynamics 1.3 Dynamics Michel A. Van Hove Michel A. Van Hove WARNING: PRINTING THIS DOCUMENT WILL USE MUCH INK AND WILL NOT SHOW ANIMATIONS.
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2 Inertia Inertia Inertia is the tendency for an object to resist change in its velocity inertia is responsible for many accidents! objects “keep going” forces are needed to slow down an object Chicago 2005
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3 Newton’s First Law – History of inertia Newton’s First Law – History of inertia Chinese scholars (in Mo Tzu) – 3rd century BC “The cessation of motion is due to the opposing force . .. If there is no opposing force . .. the motion will never stop. This is as true as that an ox is not a horse.” Aristotle (famous Greek philosopher) ~330 BC “In the absence of a force, all objects (on earth) would naturally come to rest in a state of no movement, and moving objects only continue to move so long as there is a force inducing them to do so.” This described everyday life and was consistent with the view that the earth was stationary and at the centre of the universe. Different laws were presumed to apply to heavenly objects. Despite being challenged several times, this view persisted for almost 2000 years.
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4 Newton’s First Law – History of inertia Newton’s First Law – History of inertia Joannes Philoponus (Greek philosopher of Alexandria) – 6th century AD First criticised Aristotle's view: “Motion is maintained by some property of the object, imparted when it was set in motion.” Jean Buridan (French priest) – 14th century AD He rejected the idea that the property of a moving object (which he named impetus ) disappeared spontaneously. Instead, “a moving object would be stopped by the forces of air resistance and gravity which might oppose its impetus.” However, his ideas were still mixed and confused. He still kept many of Aristotle’s views and believed there was something different between moving objects and objects at rest. Impetus could be linear or circular.
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5 Newton’s First Law – History of inertia Newton’s First Law – History of inertia Nicolaus Copernicus (famous Polish astronomer) – 1514 He developed his theories on the heliocentric (Sun centred) Universe: the Earth is not at rest but in orbit around the Sun. This was in opposition to Aristotle’s theories. Galileo Galilei (famous Italian astronomer) ~1600 He accepted Copernicus’ model of the universe and concluded that it was the nature of an object to resist changes in its motion : “Any velocity once imparted to a moving body will be rigidly maintained as long as the external causes of retardation are removed.” He later wrote that it is impossible to tell the difference between a moving object and a stationary one without some outside reference to compare it against – beginnings of relativity!
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6 Newton’s First Law – History of inertia Newton’s First Law – History of inertia
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This note was uploaded on 01/11/2011 for the course AP 1200 taught by Professor Michela.vanhove during the Spring '10 term at City University of Hong Kong.

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AP1200_Ch1_Mechanics-3Dynamics-2007 - AP1200 1. Mechanics...

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