| English | Free fall |
|---|---|
| Bahasa Melayu | Jatuh bebas |
| 中文 | 自由落体 |
Definition
The motion of an object falling under the action of gravity alone, with no air resistance.
In exam terms
Free fall is the motion of an object falling under the action of gravity alone, with no air resistance acting on it. Every object in free fall has the same downward acceleration, the gravitational acceleration g ≈ 9.81 m s⁻² (often taken as 10 m s⁻² in calculations), whatever its mass.
You solve free-fall problems using the equations of motion with a = g. For example, a stone dropped from rest reaches a velocity v = u + gt = 0 + (10 m s⁻² × 3 s) = 30 m s⁻¹ after 3 s.
Do not confuse it with ordinary falling
Do not confuse free fall with ordinary falling through air. In real air, air resistance acts upward and grows with speed until it balances weight, so the object reaches a constant terminal velocity and its acceleration becomes zero.
In true free fall there is no air resistance, so acceleration stays equal to g throughout.
In Paper 2 this appears as explain why a coin and a feather fall together in a vacuum: with no air resistance both have the same acceleration g regardless of mass.
Source: DSKP KSSM Physics Form 4 and 5 (Versi English) (Bahagian Pembangunan Kurikulum (BPK), KPM)