Acceleration is defined as the rate of change of velocity. The important thing to realise here is that velocity is a vector quantity while speed is a scalar one. An object going in circular motion has constant speed at every point on the circle but the *velocity is changing *because the direction at which the object is moving is changing. The velocity is always tangential to the path defined by the movement. So, because the velocity is changing at every point, this means that there is a change of velocity at time progresses. By the previously mentioned definition of acceleration, the object experiences a change of velocity at different time intervals and thus is said to be accelerating. The acceleration of the object at every point is towards the centre of the circle.