Circular Motion (AQA A Level Physics): Revision Note

Circular motion

• Velocity and acceleration are both vector quantities

• An object in uniform circular motion has a constant linear speed

• However, it is continuously changing direction

• Since velocity is the speed in a given direction, it, therefore, has a constantly changing velocity

  • The object therefore must be accelerating

  • This is because acceleration is defined as the rate of change of velocity

• This acceleration is called the centripetal acceleration and is perpendicular to the direction of the linear speed

  • Centripetal means it acts towards the centre of the circular path

• The centripetal acceleration is caused by a centripetal force of constant magnitude that also acts perpendicular to the direction of motion (towards the centre)

  • This is a result of Newton's second law

• Therefore, the centripetal acceleration and force act in the same direction