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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

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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 Weight？

又称： vertical

Definition 24.1 Primary & Middle School Physics · 第 24 章 — Weight and Mass

The weight of a thing is the force with which the Earth pulls it downward. Weight is what your arm fights when you hold a bucket, and what stretches the spring when the bucket hangs from it. Like every force, weight has a direction: straight down, always.

示例

Example 24.3 (Cousins, not twins)

Mass answers: how much stuff? It is a property of the thing alone — the same in your hand, underwater, or on the Moon. Weight answers: how hard is it pulled down here? It depends on the thing and on where it is. Change nothing but the place, and the mass stays; the weight can change.

Example 24.6 (The Moon is a weaker puller)

The Moon is much smaller than the Earth, and it pulls things far more weakly — about six times more weakly. An astronaut’s pack keeps every gram of its mass on the trip, but its weight up there shrinks to a sixth. That is the whole secret of the bouncing: legs trained to fight Earth-pull suddenly fight a gentle Moon-pull, and every step becomes a leap.

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Definition 4.9 High School Physics · 第 4 章 — Universal Gravitation and Weight

The weight $\vect P$ of an object at the surface of a star (a planet, a moon, …) is the gravitational force the star exerts on it. It points toward the star’s center — the direction we call vertical — and is measured in newtons.

示例

Example 4.6 (Two friends)

Two $70\,\mathrm{kg}$ friends stand with their centers $1.0\,\mathrm{m}$ apart:

F = 6.67 \times 10^{-11} \times \frac{70 \times 70}{1.0^2} \approx 3.3 \times 10^{-7}\,\mathrm{N}.

Each friend’s weight is about $6.9 \times 10^{2}\,\mathrm{N}$ — two billion times larger. Their mutual attraction is real, but hopeless to feel.

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