# What is angular and linear velocity

## Circular movements¶

### Circular movements with constant acceleration¶

In the same way as an acceleration a change in speed of a body causes angular acceleration a change in angular velocity of a body.

Between the angular acceleration and that in time caused change in angular velocity the following relationship applies:

The angular acceleration, like the angular velocity, is a vector quantity. If, for example, a horizontal disk is accelerated counterclockwise, the angular acceleration points upwards, otherwise it points downwards.  In general, the “right-hand rule” can be used again: If the fingers of the right hand point in the direction of acceleration, the thumb shows the direction of the angular acceleration.

Since when moving on a circular path, the radius does not change, there is another relationship between the angular acceleration and the ordinary tangential acceleration :

For the angle of rotation passed through during the accelerated circular movement also applies in analogy to accelerated linear motion:

Here there the initial angle of the circular motion.

Angular accelerations always occur on a rotating object when there is a resulting torque acts on the object; applies to the angular acceleration , in which stands for the moment of inertia of the object.

Remarks: