| English | Centripetal force |
|---|---|
| Bahasa Melayu | Daya memusat |
| 中文 | 向心力 |
Definition
The net force directed towards the centre of a circle that keeps an object moving in a circular path, such as a satellite in orbit.
In exam terms
Centripetal force is the net force directed towards the centre of a circle that keeps an object moving in a circular path. It is a resultant force, not a new kind of force, and it is measured in newtons (N).
Its size is given by F = mv²/r, where m is the mass, v the speed and r the radius. For example, for a satellite the gravitational pull acts as the centripetal force; for a ball on a string the tension does.
A 0.5 kg ball moving at 4 m s⁻¹ on a 2 m string needs F = mv²/r = 0.5 kg × (4 m s⁻¹)² ÷ 2 m = 4 N directed towards the centre.
Do not confuse it with…
Do not confuse centripetal force with the so-called centrifugal force. Centripetal force is a real force acting towards the centre; the outward push a passenger seems to feel is not a real force acting on the object but the result of inertia carrying it in a straight line while the seat pushes it inward.
In Paper 2 this is asked as state the direction of the centripetal force or explain what provides the centripetal force in a given situation. Always name the actual force (tension, gravity, friction) that acts towards the centre, and state that it points to the centre of the circle.
Source: DSKP KSSM Physics Form 4 and 5 (Versi English) (Bahagian Pembangunan Kurikulum (BPK), KPM)