| English | Momentum |
|---|---|
| Bahasa Melayu | Momentum |
| 中文 | 动量 |
Definition
The product of the mass and velocity of an object; a vector quantity (momentum = mass × velocity), measured in kg m s⁻¹.
In exam terms
Momentum is the product of the mass and the velocity of a moving object. It is a vector, symbol p, SI unit the kilogram metre per second (kg m s⁻¹), given by momentum = mass × velocity (p = mv), and it points in the same direction as the velocity.
For example, a 2 kg trolley moving at 5 m s⁻¹ to the right has momentum p = 2 kg × 5 m s⁻¹ = 10 kg m s⁻¹ to the right. Because it is a vector, direction matters when momentum before and after a collision are compared.
Do not confuse it with kinetic energy
Do not confuse momentum with kinetic energy. Momentum is a vector p = mv in kg m s⁻¹; kinetic energy is a scalar E = ½mv² in joules (J).
In a collision total momentum is always conserved, while kinetic energy is only conserved in an elastic collision.
In Paper 2 you may be asked to calculate the momentum of an object or to apply the principle of conservation of momentum, so keep track of direction by taking one direction as positive.
Source: DSKP KSSM Physics Form 4 and 5 (Versi English) (Bahagian Pembangunan Kurikulum (BPK), KPM)