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Unformatted text preview: 1 Center of Mass, Reference Frames Physics 1301, Fall 2011: Class 17 Tuesday, October 11, 2011 2 Objectives: Tuesday, October 11 • Center of mass • Reference frames 3 Demonstrations Center of Mass • The response of an extended body to forces and torques depends on how the mass is distributed in the body • A useful (but not complete) description is to characterize the body in terms of 3 parameters • Mass (does not depend on distance) • Center of Mass (depends on distance) • Moment of Inertia (depends of distance squared) 4 Mass, CM, Moment of Inertia 5 M = m i i = 1 n ∑ M = ρ dV ∫ x cm = 1 M m i i = 1 n ∑ r i x cm = 1 M ρ r dV ∫ I = m i i = 1 n ∑ r i 2 I = ρ r 2 dV ∫ Example • An object consists of three small spheres located at the centers of an equilateral triangle 10.0 cm on a side connected by very light rods. Each sphere has a mass of 1.00 kg. One of the spheres is located at the origin. What are the coordinates of the cm? 6 (0,0) (?,?) (?,?) (a) (0,0) (b) (10,0) (c) (10,10) (d) (5, 8.66) (e) (5,2.89) Example • An object consists of three small spheres located at...
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 Fall '08
 Marshak
 Physics, Center Of Mass, Centrifugal Force, Force, Mass, Special Relativity, Frame of reference, Inertial frame of reference

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