# AQA A-Level Physics/Circular Motion

Circular Motion- When an object moves in a circle at a constant speed, its velocity (which is a vector) is constantly changing. This is not because the magnitude of the velocity is changing, but because the direction is. This constantly changing velocity means that the object is accelerating (due to centripetal acceleration). For this acceleration to happen, there must be a resultant force, and the resultant force is called the centripetal force.

Angular Speed: The angular speed of an object is the angle it moves through measured in radians divided by the time taken to move through that angle. This means that the unit for angular speed is the radians per second.

V is the linear velocity measured in metres per second

r is the radius of the circle in metres

f is the frequency of rotation in hertz

Centripetal Acceleration: Centripetal acceleration is measured in metres per second squared. It is always directed towards the centre of the circle.

Centripetal Force: When an object moves in a circle, the centripetal force always acts towards the centre of the circle. The centripetal force, measured in Newtons can be different forces in different settings it can be gravity, friction, tension, lift, electrostatic attraction or a mix of several.