| English | Universal gravitational constant |
|---|---|
| Bahasa Melayu | Pemalar graviti semesta |
| 中文 | 万有引力常数 |
Definition
The universal constant G in Newton's law of gravitation, with a value of about 6.67 × 10⁻¹¹ N m² kg⁻².
In exam terms
The universal gravitational constant, symbol G, is the constant of proportionality in Newton's law of gravitation, F = GMm/r². Its value is about 6.67 × 10⁻¹¹ N m² kg⁻², and it is the same everywhere in the universe.
Its unit follows from the equation: rearranging gives G = Fr²/(Mm), so the unit is N m² kg⁻². For example, the very small value of G explains why the gravitational force between two everyday objects is far too weak to notice, while the force between huge masses such as the Earth and the Moon is large.
Do not confuse it with…
Do not confuse the gravitational constant G with the gravitational field strength g. G is a universal constant with the unit N m² kg⁻², the same everywhere; g is the force per unit mass at a point, with the unit N kg⁻¹, and it changes with location, being about 9.81 N kg⁻¹ near the Earth's surface.
In Paper 2 this is asked as state the value and unit of G or explain the difference between G and g. A common error is to write the unit of G as N kg⁻¹; the correct unit is N m² kg⁻², derived from F = GMm/r².
Source: DSKP KSSM Physics Form 4 and 5 (Versi English) (Bahagian Pembangunan Kurikulum (BPK), KPM)