| English | Newton's universal law of gravitation |
|---|---|
| Bahasa Melayu | Hukum kegravitian semesta Newton |
| 中文 | 万有引力定律 |
Definition
Every mass attracts every other mass with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between their centres.
In exam terms
Newton's universal law of gravitation states that every mass attracts every other mass with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between their centres. It is written F = GMm ÷ r².
Here F is the gravitational force in newtons (N), M and m are the two masses in kilograms (kg), r is the distance between their centres in metres (m), and G is the universal gravitational constant, about 6.67 × 10⁻¹¹ N m² kg⁻². Doubling the separation r reduces the force to a quarter, because of the inverse-square relationship.
Do not confuse it with…
Do not confuse Newton's law of gravitation (F = GMm ÷ r², the attraction between two masses) with gravitational field strength (g = GM ÷ r², the force per kilogram at a point). The first gives a force in newtons; the second gives a field strength in N kg⁻¹.
In Paper 2 you may be asked to state the law in words, or to explain why the force between planets is still large despite the small value of G. Point to the enormous masses M and m, which more than make up for the tiny constant.
Source: DSKP KSSM Physics Form 4 and 5 (Versi English) (Bahagian Pembangunan Kurikulum (BPK), KPM)