The disc has linear velocity and rotates

To get the speed out of a velocity vector, you need to calculate the norm of the vec-tor, as shown in Equation 20.4.

Equation 20.4

You can calculate angular velocity using Equation 20.5.

Equation 20.5

You have now arrived at acceleration. Acceleration is an important concept to know because you will use it to actually move your objects after you apply forces to them.

As with the velocity, there are two types of acceleration: linear and angular.

Linear acceleration is the change of linear velocity in a period of time, similar to linear velocity. If you accelerate a car by ten meters in a second, you will change the car’s velocity from the current velocity to the current velocity plus ten after one second.

You can calculate the acceleration by using the methods shown in Equations 20.6 and 20.7.

→Acceleration = (→CurrentVelocity −→LastVelocity) /

(CurrentTime − LastTime)

velocity, angular velocity.

To determine angular acceleration, use Equation 20.8.