Velocity Magnitude (VM)
Returns the magnitude of the first time-derivative of the displacement vector between two coordinate system markers.
Format
VM (To Marker, From Marker, Reference Frame)
Arguments
To Marker | (Required) The coordinate system marker whose velocity is being measured. |
From Marker | (Optional) The coordinate system marker whose velocity is subtracted off. If you don't specify this argument, it defaults to the global origin. |
Reference Frame | (Optional) The coordinate system marker in which the time derivatives are calculated. If you don't specify this argument, it defaults to the ground reference frame. |
Equation
Mathematically, VM is calculated as follows:
.where:
■
is the position vector from the global origin to the To Marker, T.
is the position vector from the global origin to the To Marker, T.■
is the time-derivative of 
with respect to the Reference Frame, R.
is the time-derivative of with respect to the Reference Frame, R.■
is the position vector from the global origin to the From Marker, F.
is the position vector from the global origin to the From Marker, F.■
is the time-derivative of 
with respect to the Reference Frame, R.
is the time-derivative of with respect to the Reference Frame, R.Example
The following function returns the magnitude of the velocity vector between marker_T and marker_F. The vector time-derivative is taken in the reference frame of marker_R.
VM(marker_T, marker_F, marker_R)