Circular Motion

This lesson covers the physics of objects moving in circles, including centripetal force and centripetal acceleration — as required by the Edexcel GCSE Physics specification (1PH0), Topic 2: Motion and Forces. You need to understand why a force is needed for circular motion, what provides that force in different situations, and why velocity changes even when speed is constant.

---

Objects Moving in Circles

When an object moves in a circle at constant speed, it might seem like nothing is changing — but its velocity is constantly changing. This is because velocity is a vector quantity (it has both magnitude and direction), and the direction of a moving object in a circle is always changing.

Key Distinction: Speed vs Velocity

Quantity	Type	What It Measures
Speed	Scalar	How fast (magnitude only)
Velocity	Vector	How fast AND in which direction

An object moving in a circle at constant speed has a constantly changing velocity because its direction changes at every point along the circle.

---

Centripetal Acceleration