| English | Limit of proportionality |
|---|---|
| Bahasa Melayu | Had kekadaran |
| 中文 | 比例极限 |
Definition
The point up to which the extension of a spring stays directly proportional to the applied force.
In exam terms
The limit of proportionality is the point up to which the extension of a spring stays directly proportional to the applied force. Below it, Hooke's law F = kx holds and a force–extension graph is a straight line through the origin.
At the limit of proportionality the graph stops being straight, so extension is no longer proportional to force.
For example, if a spring's force–extension graph is a straight line up to 10 N and then curves, the limit of proportionality is at 10 N. It has no special unit of its own; the force at that point is in newtons (N) and the extension in metres (m).
Don't confuse it with the elastic limit
Do not confuse the limit of proportionality with the elastic limit. The limit of proportionality is where the straight-line relationship ends; the elastic limit, usually just beyond it, is where the spring stops returning to its original length.
A spring can pass the limit of proportionality yet still be elastic for a little further.
In Paper 2 this is usually asked with 'Define…' or 'Mark the limit of proportionality on the graph'. Identify it as the end of the straight-line region, and read the force there in newtons (N).
Source: DSKP KSSM Physics Form 4 and 5 (Versi English) (Bahagian Pembangunan Kurikulum (BPK), KPM)