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1 Primary & Middle School Mathematics1–9 年级在线 2 High School Mathematics10–12 年级在线 3 University Mathematics — Year 1本科一年级在线 4 University Mathematics — Year 2本科二年级在线 5 University Mathematics — Year 3本科三年级在线

1 Primary & Middle School Physics1–9 年级在线 2 High School Physics10–12 年级在线 3 University Physics — Year 1本科一年级在线 4 University Physics — Year 2本科二年级在线 5 University Physics — Year 3本科三年级在线

1 School Chemistry — Grades 1 to 121–12 年级在线 2 University Chemistry — Year 1本科一年级在线 3 University Chemistry — Year 2本科二年级在线 4 University Chemistry — Year 3本科三年级在线

1 Primary & Middle School Biology1–9 年级在线 2 High School Biology10–12 年级在线 3 University Biology — Year 1本科一年级在线 4 University Biology — Year 2本科二年级在线 5 University Biology — Year 3本科三年级在线

1 Primary & Middle School Earth and Space Sciences1–9 年级在线 2 High School Earth and Space Sciences10–12 年级在线 3 University Earth and Space Sciences — Year 1本科一年级在线 4 University Earth and Space Sciences — Year 2本科二年级在线 5 University Earth and Space Sciences — Year 3本科三年级在线

1 Markets I: The Ecosystem and Exchange-Traded Markets市场在线 2 Markets II: Rates, FX and Credit市场在线 3 Markets III: Commodities, Energy and Crypto市场在线 4 Quantitative Methods方法在线 5 Derivatives and Volatility衍生品在线 6 Rates, Credit, XVA and Risk利率、信用与风险在线 7 Research Craft: Predictors, Backtests, Measurement, Portfolios研究在线 8 Strategies I: Equities and Futures策略在线 9 Strategies II: Volatility, Relative Value, Macro and the Bank Desks策略在线 10 Microstructure and Execution交易执行在线 11 Market Making and High-Frequency Trading做市在线 12 Machine Learning for Markets机器学习在线 13 Low-Latency Software技术在线 14 Networks, Hardware and Trading Infrastructure技术在线 15 Research, Data and Risk Platforms技术在线 16 The Desk and the Firm公司运营在线 17 The Industry: Firms, Roles and Careers职业发展在线 18 Interviews I: Maths, Probability and Speed职业发展在线 19 Interviews II: Markets, Trading Games and the Final Round职业发展在线 20 Interviews III: Code职业发展在线

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Physics · 术语表

什么是 The second？

又称： second

Definition 8.7 Primary & Middle School Physics · 第 8 章 — Measuring Time

The second is the unit of time used all over the world, written $\mathrm{s}$ . One second is about one calm heartbeat, or the steady tick of a big clock. Saying “one little crocodile, two little crocodiles” at a calm pace counts roughly one second per crocodile.

Two clocks: the short hand tells the hour. At half past three, it has walked halfway from the 3 toward the 4. — Two clocks: the short hand tells the hour. At half past three, it has walked halfway from the $3$ toward the $4$ .

示例

Example 8.8 (Try it: how many seconds?)

Count seconds steadily while: you hold your breath comfortably; the tap fills a glass; a friend runs to the fence and back. The glass might take $6$ seconds, the run $20$ . Now the tooth-brushing and the song from before can get numbers — and numbers, as with lengths, can travel and be checked.

Example 8.9 (Hours on the clock)

Seconds are for short things. Long stretches are counted in hours: school mornings last hours, a night of sleep too. The clock’s short hand points to the hour: straight at the $3$ , it is three o’clock; between $3$ and $4$ with the long hand pointing straight down, it is half past three. A whole day and night together hold $24$ hours — while the Earth, remember, makes one full turn.

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