| English | Hooke's law |
|---|---|
| Bahasa Melayu | Hukum Hooke |
| 中文 | 胡克定律 |
Definition
Within the elastic limit, the extension of a spring is directly proportional to the force applied to it.
In exam terms
Hooke's law states that, within the elastic limit, the extension of a spring is directly proportional to the force applied to it. Written as an equation, F = kx, where F is the force in newtons (N), x is the extension in metres (m) and k is the spring constant in newtons per metre (N m⁻¹).
A force–extension graph is therefore a straight line through the origin while the law holds.
For example, a spring with a spring constant of 20 N m⁻¹ stretched by 0.10 m needs a force F = 20 N m⁻¹ × 0.10 m = 2.0 N. Double the force and the extension doubles too.
Don't confuse it with the elastic limit
Do not confuse Hooke's law with the elastic limit. Hooke's law is the proportional relationship F = kx; the elastic limit is the point beyond which a spring no longer returns to its original length, so the law also stops applying there.
It is also different from the limit of proportionality, the point where the straight-line relationship first bends.
In Paper 2 this is usually asked with 'State Hooke's law' or by giving a force–extension graph whose straight-line gradient is the spring constant. Read the gradient with units, for example N m⁻¹.
Source: DSKP KSSM Physics Form 4 and 5 (Versi English) (Bahagian Pembangunan Kurikulum (BPK), KPM)