تفلطح استوائي
التفلطح الإستوائي Equatorial bulge هوزيادة القطر الاستوائي لجرم كوني نجم أوكوكب سيار على القطر القطبى وذلك نتيجة الدوران المحورى للجرم .
Fixed to the vertical rod is a spring metal band. When stationary the spring metal band is circular in shape. The top of the metal band can slide along the vertical rod.
When spun, the spring-metal band bulges at its equator and flattens at its poles in analogy with the Earth.
When spun, the spring-metal band bulges at its equator and flattens at its poles in analogy with the Earth.
التفلطح القطبي
التفلطح القطبي هوانبعاج عند القطبين أوتسطح عند قطبي جرم كروي.
الاختلافات في تسارع الجاذبية
The forces at play in the case of a planet with an equatorial bulge due to rotation.
Red arrow: gravity
Green arrow, the normal force
Blue arrow: the resultant force
The resultant force provides required centripetal force. Without this centripetal force frictionless objects would slide towards the equator.
In calculations, when a coordinate system is used that is co-rotating with the Earth, the vector of the fictitious centrifugal force points outward, and is just as large as the vector representing the centripetal force.
Red arrow: gravity
Green arrow, the normal force
Blue arrow: the resultant force
The resultant force provides required centripetal force. Without this centripetal force frictionless objects would slide towards the equator.
In calculations, when a coordinate system is used that is co-rotating with the Earth, the vector of the fictitious centrifugal force points outward, and is just as large as the vector representing the centripetal force.
مدارات الأقمار الصناعية
الأجرام السماوية الأخرى
| Body | Equatorial diameter | Polar diameter | Equatorial bulge | Flattening ratio |
|---|---|---|---|---|
| Earth | 12,756.28 km | 12,713.56 km | 42.72 km | 1:298.2575 |
| Mars | 6,805 km | 6,754.8 km | 50.2 km | 1:135.56 |
| Ceres | 975 km | 909 km | 66 km | 1:14.77 |
| Jupiter | 143,884 km | 133,709 km | 10,175 km | 1:14.14 |
| Saturn | 120,536 km | 108,728 km | 11,808 km | 1:10.21 |
| Uranus | 51,118 km | 49,946 km | 1,172 km | 1:43.62 |
| Neptune | 49,528 km | 48,682 km | 846 km | 1:58.54 |
أنظرأيضا
- فلطحة
- Flattening
- Reference ellipsoid
- Oblate
المصادر
- مؤمن, عبد الأمير (2006). قاموس دار الفهم الفلكي. بيروت، لبنان: دار الفهم للملايين.
- Solar System Formation, Accretion, and the Early Thermal State of the Earth
(PDF-file, 312 KB) Available as part of the MIT OpenCourseWare initiative
