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Download FORCE AND MOTION I Change in velocity acceleration Q
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FORCE AND MOTION I • Change in velocity acceleration Q: What causes acceleration? An interaction that can cause an acceleration of a body is called a force. The force is said to act on the body Isaac Newton (1642-1727) Provided an understanding of the relation between force and acceleration. • It does not apply to all situations -Objects moving close to speed of light -Physics of the atomic scale objects such as electrons Newtonian Mechanics Three primary laws Newton’s First Law • Before Newton it was thought force is needed to keep a body moving Galileo Newton’s First Law If no force acts on a body, it’s velocity can not change If it is at rest, it stays at rest. If it is moving with a velocity, it will continue tobe moving with the same velocity. FORCE The force needed to accelerate a body of 1 kg mass with acceleration of 1 m/s2 is 1 Newton (1 N) Q: Is force a vector quantity? Yes, it has both magnitude and direction. Q: If two or more forces acting on a body, what happens? There will be a net force or resultant force determined by adding the forces vectorially. Newton’s First Law If no net force acts on a body (Fnet=0), then the body’s velocity can not change no acceleration. An inertial reference frame is one in which Newton’s first law holds. Mass • Mass is an intrinsic characteristic of a body. • Mass is a scalar quantity. • The mass relates a force on the body to the resulting acceleration. Newton’s Second Law The net force on a body is equal to the product of the body’s mass and the acceleration of the body. Vector sum of all the forces act on the body. Units?
