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PHY.7:3 - Forces
| Force | Tension |
|---|
| Compact principle and physical content | One scalar can generate several equations, but every consequential interaction still needs a physical basis. |
| Convenient coordinates and retained motion | Eliminating a constraint can simplify the calculation while concealing a moving support or an omitted degree of freedom. |
| Interior equations and boundaries | Integration by parts exposes both; the physical preparation decides which boundary variations remain free. |
| Mathematical comparison and physical evolution | Nearby histories define a variation; the predicted motion is selected and used with its own preparation. |
| Reusable formalism and cost | A common derivation helps repeated changes, while a direct balance may obtain one consequence with less work. |