# How do gyroscopic instruments work? [closed]

I'm trying to better my understanding of the physics behind gyroscopic instruments in an aircraft. I am aware that a spinning gyroscope creates rigidity in space by resisting applied forces. But, what exactly is the resistive force acting on the externally applied to forces, and how is it created? Is that what precession is?

• I'm voting to close this question as off-topic. This question would be better on Physics.SE The answer is inertia in the spinning plan (conservation of angular momentum).
– mins
Dec 10 '15 at 6:32
• Yeah your probably right. Didn't cross my mind, I just came straight here. Dec 10 '15 at 6:36

I saw this pretty cool video a while ago:

It gives an intuitive discussion of gyroscopes.

On another level though, it boils down to the angular momentum of the spinning gyroscope, and the fact that in order to change that momentum's direction/magnitude, an external moment must be applied.

Gyroscopes basically work by the principle of conservation of angular momentum. Consider a gyroscope (or a spinning wheel) in space like shown below:

Image from pigeonsnest.co.uk

Consider the wheel in the center spinning at an angular velocity $\omega$, so that the spin angular momentum is $I\omega$, along the X axis. Now, consider a torque applied $\mathcal{T}$ along the Z axis.

Now, the resultant of these two makes the spin axis to align along the axis A'. Basically, the spin angular momentum 'chases' the torque in the same plane. This is the basis of gyroscopic precession.

See Prof. Walter Lewin's lecture on Rolling motion and gyroscopes for a thorough explanation.