Ch4 - Chapter 4 The Laws of Motion Classes of Forces Contact forces involve physical contact between two objects Field forces act through empty

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Chapter 4 The Laws of Motion
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Classes of Forces Contact forces involve physical contact between two objects Field forces act through empty space No physical contact is required
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More About Forces A spring can be used to calibrate the magnitude of a force Forces are vectors, so you must use the rules for vector addition to find the net force acting on an object
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Newton’s First Law If an object does not interact with other objects, it is possible to identify a reference frame in which the object has zero acceleration This is also called the law of inertia It defines a special set of reference frames called inertial frames , We call this an inertial frame of reference
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Inertial Frames Any reference frame that moves with constant velocity relative to an inertial frame is itself an inertial frame A reference frame that moves with constant velocity relative to the distant stars is the best approximation of an inertial frame We can consider the Earth to be such an inertial frame although it has a small centripetal acceleration associated with its motion
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Newton’s First Law – Alternative Statement In the absence of external forces, when viewed from an inertial reference frame, an object at rest remains at rest and an object in motion continues in motion with a constant velocity Newton’s First Law describes what happens in the absence of a force Also tells us that when no force acts on an object, the acceleration of the object is zero
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Inertia and Mass The tendency of an object to resist any attempt to change its velocity is called inertia Mass is that property of an object that specifies how much resistance an object exhibits to changes in its velocity
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More About Mass Mass is an inherent property of an object Mass is independent of the object’s surroundings Mass is independent of the method used to measure it Mass is a scalar quantity The SI unit of mass is kg
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Mass vs. Weight Mass and weight are two different quantities Weight is equal to the magnitude of the
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This note was uploaded on 04/02/2010 for the course PHYSICS 6A taught by Professor Koskeshian during the Spring '10 term at UCLA.

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Ch4 - Chapter 4 The Laws of Motion Classes of Forces Contact forces involve physical contact between two objects Field forces act through empty

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