Physics II workshop_Part_50

# Physics II workshop_Part_50 - Even if you are not actually...

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102 Week #9

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103 Center of Mass of a Group of Particles At first sight, calculating the motion of an extended object (such as a javelin) or a group of particles (such as debris from an explosion) seems complicated. But we can make life easier by following only the motion of the center of mass of the system. Thus, we can determine the motion of a javelin by applying Newton’s Laws to its center of mass, rather than calculating the motion of each individual point. In 2-dimensions, the center of mass of a group of N point masses (particles) is r R CoM = X CoM ˆ i + Y CoM ˆ j where X CoM = x i m i i = 1 N m i i = 1 N and Y CoM = y i m i i = 1 N m i i = 1 N are the x- and y- components of the center of mass, respectively.
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Unformatted text preview: Even if you are not actually dealing with particles, it is often possible to treat objects as if they are point masses, if they are uniform and symmetric (e.g., its obvious that the center of mass of a uniform disk must be at its center), or if you are trying to find the CoM of objects which are small compared to their distance apart (e.g., Earth and Moon). OK, so here’s the Earth and Moon. Where is the CoM? You will find the relevant data in the Appendix in your textbook. Take the origin of the x-axis to be the center of the Earth. Is the CoM inside or outside the Earth? D Earth Moon...
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## This note was uploaded on 11/26/2011 for the course PHY 2053 taught by Professor Lind during the Fall '09 term at FSU.

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Physics II workshop_Part_50 - Even if you are not actually...

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