wiki:link_for_instructors

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wiki:link_for_instructors [2019/11/12 10:51] ethanminot [Reflections from Fall 2019] |
wiki:link_for_instructors [2019/12/15 12:34] (current) ethanminot [Reflections from Fall 2019] |
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https://physicstoday.scitation.org/doi/10.1063/PT.3.4042 | https://physicstoday.scitation.org/doi/10.1063/PT.3.4042 | ||

- | Emilie du Chatelet (conservation of energy, pairs well with Emmy Noether): | + | Emilie du Chatelet (conservation of energy, pairs well with Emmy Noether). |

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+ | In the final exam I notice reliance on a technique students have invented for themselves to circumvent physical reasoning. I've heard students call it "unit analysis". The basic idea: The problem gives some numbers to solve the problem. Mash these numbers together in a way that gives the desired units. Here is a cautionary tale of how badly this approach can fail. | ||

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+ | **Estimate the lifetime of the Sun in unit of seconds:** First, piece together some facts about the Sun. The fusion of hydrogen atoms produces 1.3 x 10^12 kg.m²/s² of energy per atom. The surface area of the Sun is 4πR². The mass of the hydrogen fuel is 2 x 10^29 kg. Put these three quantities together and take the square root. Then I have something with dimensions of time (//t// = 2 x 10^30 seconds). Is this the lifetime of the Sun? | ||

====== Reflections from Winter 2017 ====== | ====== Reflections from Winter 2017 ====== |

wiki/link_for_instructors.txt · Last modified: 2019/12/15 12:34 by ethanminot

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