Dear Students,

Here, I would like to specify one matter!

When we measure something in the body frame or in the inertial frame, it might be tempting to think that the axes of the body frame (x, y, z) or the inertial frame (X, Y, Z) are always measured in meters. However, that's not the case. It all depends on what you are using these axes for.

If your goal is to measure position or displacement (change of position), then the inertial and body frame axes have distance units (meters, miles, etc.). That's because your vector describes position or displacement.

If your goal is to measure velocities, the axes of the inertial and body frame axes are m/s, mph, etc. That's because now your vectors describe velocities.

If your goal is to measure angular velocities, then the axes of your inertial and body frames are measured in rad/s, degrees/s, rpm, etc. Now, your vectors describe angular velocities.

If your goal is to measure acceleration, then the axes have the units of m/s^2.

If angular acceleration, then the axes are in rad/s^2.

If torque/moment, then your vectors describe torque or moments, and therefore your axes have the units of Nm.

Best Regards,

Mark