OCR A Gateway Physics Higher tier explicitly includes circular motion as part of P2 Forces â content that AQA, Edexcel and Eduqas do not examine at GCSE. An object moving at constant speed in a circle is still accelerating, because its direction (and therefore its velocity) is constantly changing, even though its speed stays the same.
- Centripetal force is the resultant force that keeps an object moving in a circular path. It always points towards the centre of the circle, at right angles to the object's velocity.
- The centripetal force formula: F = mv²/r (F in newtons, m in kg, v in m/s, r in metres â the radius of the circle)
- A larger force is needed for a faster speed, a greater mass, or a smaller radius (tighter circle).
Applied contexts OCR A likes to use: a car going round a roundabout (friction between tyres and road provides the centripetal force), a ball on a string being swung in a horizontal circle (tension provides the centripetal force), and a banked race track corner (the track surface itself provides part of the centripetal force). Whatever the scenario, name the SPECIFIC force providing the centripetal force â "the centripetal force" alone is not a real force, it describes the role a real force (tension, friction, gravity, normal contact) is playing.
Quick Check: A 900 kg car goes around a roundabout of radius 12 m at a constant speed of 6 m/s. Calculate the centripetal force acting on it, and name the force that provides it.
F = mv²/r = 900 à 6² ÷ 12 = 900 à 36 ÷ 12 = 2700 N. The force is provided by friction between the tyres and the road surface.
This higher tier covers OCR A (J249) Higher Only: Circular Motion within Newton's Laws of Motion for GCSE Physics. Revise Newton's Laws of Motion in Forces for GCSE Physics with 24 exam-style questions and 15 flashcards. This topic shows up very often in GCSE exams, so students should be able to explain it clearly, not just recognise the term. It is section 14 of 17 in this topic. This section is most useful once the core foundation idea is secure, because it adds the detail that pushes answers higher.
Practice questions for Newton's Laws of Motion
According to Newton's First Law, what happens to an object when there is no resultant force acting on it?
A spaceship is travelling through deep space far from any planets. The engines are switched off. Explain what will happen to the motion of the spaceship and why.