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phy131studiof15:lectures:chapter13 [2015/10/10 03:50] mdawber [Rotational Kinetic Energy] |
phy131studiof15:lectures:chapter13 [2015/10/14 08:41] mdawber [Parallel axis theorem] |
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===== Parallel axis theorem ===== | ===== Parallel axis theorem ===== | ||

- | Usually a rotation axis that passes through the center of mass of an object will be one of the easiest to find the moment of inertia for, because as we saw in the last lecture the center of mass usually reflects the symmetry of the object. More moments of inertia on [[http://en.wikipedia.org/wiki/List_of_moments_of_inertia|wikipedia]]. | + | Usually a rotation axis that passes through the center of mass of an object will be one of the easiest to find the moment of inertia for, because the center of mass usually reflects the symmetry of the object. More moments of inertia on [[http://en.wikipedia.org/wiki/List_of_moments_of_inertia|wikipedia]]. |

If we know the moment of inertia of an object around an axis that passes through it's center of mass there is a theorem that can help us find the moment of inertia around a different axis parallel to the axis through the COM. | If we know the moment of inertia of an object around an axis that passes through it's center of mass there is a theorem that can help us find the moment of inertia around a different axis parallel to the axis through the COM. | ||

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The kinetic energy thus depends on the moment of inertia of the object. | The kinetic energy thus depends on the moment of inertia of the object. | ||

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+ | ===== 13.P.021 ===== | ||

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+ | ===== Hoop and Disk ===== | ||

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Suppose we release a hoop and disk from the top of a slope. They begin with the same potential energy, which one gets to the bottom of the slope first? | Suppose we release a hoop and disk from the top of a slope. They begin with the same potential energy, which one gets to the bottom of the slope first? | ||

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$\Sigma \tau=I \alpha=\frac{dL}{dt}$ | $\Sigma \tau=I \alpha=\frac{dL}{dt}$ | ||

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+ | ===== 13.P.048 ===== | ||

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===== Conservation of angular momementum ===== | ===== Conservation of angular momementum ===== |