| English | Gravitational field strength |
|---|---|
| Bahasa Melayu | Kekuatan medan graviti |
| 中文 | 引力场强度 |
Definition
The gravitational force acting on each kilogram of mass at a point in a field; measured in newtons per kilogram (N kg⁻¹).
In exam terms
Gravitational field strength is the gravitational force acting on each kilogram of mass at a point in a field. It is a vector directed towards the mass and its SI unit is the newton per kilogram (N kg⁻¹).
It is found from g = F ÷ m.
Here F is the gravitational force in newtons (N) and m is the mass in kilograms (kg). For example, a 2 kg object with weight 19.6 N sits in a field of g = F ÷ m = 19.6 N ÷ 2 kg = 9.8 N kg⁻¹.
Numerically this value also equals the gravitational (free-fall) acceleration in m s⁻².
Do not confuse it with…
Do not confuse gravitational field strength (g in N kg⁻¹, force per unit mass) with weight (W in N, the force itself). Weight = mass × field strength, so the field strength is what is left after you divide the weight by the mass.
In Paper 2 you may be asked to define gravitational field strength, or to calculate it from a given weight and mass. Note that although g near Earth is written as 9.81 N kg⁻¹ or 9.81 m s⁻², the two units describe the same quantity in different roles.
Source: DSKP KSSM Physics Form 4 and 5 (Versi English) (Bahagian Pembangunan Kurikulum (BPK), KPM)