EP Chap9 - Hints P4 Break into three sections. Then replace...

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1 Chap 9 Center of mass and linear momentum Note – this is an outline of the lecture, print this and take notes on it in lecture It is not the and take notes on it in lecture. It is not the complete lecture. You should attend lecture to get the complete notes Images taken from Halliday/Resnick/Walker, Fundamentals of Physics, 7 th Edition, John Wiley and Sons Inc., by permission. Hints P4 Break into three sections. Then replace each of these three section by a point mass. P15 First find location where shell explodes. Then use conservation of momentum along horizontal to find velocity of other (2 nd ) fragment after explosion. Use this new velocity to find where the second fragment lands. P35 Use conservation of momentum if you think the external force is zero external force is zero. P50. Use conservation of momentum to find the velocity of the block after the bullet emerges. Now find the height to which the block rises. P60. Apply conservation of energy to find the speed of the ball just before it strikes the block. Now use your understanding of collisions to find the speed of the ball and block just after the collision. The Center of Mass (com) Com :balance point of an object :point on object that moves in a parabolic arc when object is thrown The Center of Mass-point masses 2 2 1 1 2 1 2 2 1 1 2 2 1 1 2 1 2 2 1 1 com com M y m y m m m y m y m y M x m x m m m x m x m x + = + + = + = + + = j ˆ i ˆ com com com y x r + = v The Center of mass: e.g. see-saw SP9-1 The particles below form an equilateral triangle of edge length a = 140 cm. Where is the center of mass of this system?
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2 Solid bodies Have to rewrite the sums as integrals = = = = = = xdV V dV x V ydm M y xdV V dV x V xdm M x com com 1 1 1 1 1 1 ρ Most objects we deal with are symmetric e.g. com of a uniform disc is located at its center e.g. com of a uniform rod is located at its middle For these cases we do not have to do the integrals! Newton's 2 nd Law for a System of Particles F net :sum of all external forces that act on com net a m F v v = the system Internal forces are not included.
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This note was uploaded on 04/07/2008 for the course PHYS 213 taught by Professor Oshea during the Spring '08 term at Kansas State University.

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EP Chap9 - Hints P4 Break into three sections. Then replace...

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