Gyroscope Principles Rigidity is the ability of a freely rotating mass to maintain its plane of spin when any external force is applied to it. First Law Of Gyroscopes: If a rotating wheel is so maintained as to be free to move about any axis passing through its centre of mass, its spin axis will remain fxed in space. Second Law Of Gyroscopes: When a torque acts on a spinning mass with an axis perpendicular to that of spin, then the latter will precess about an axis perpendicular to both aforementioned axes, at an angular velocity, Ω, = T/Iω. Referring to Figure 1: Angular momentum of system = Ω Angular momentum of rotor = Iω (I = moment of inertia; ω = angular velocity) Torque = T In time δt the spin axis moves through δθ. ∴δθ = Ωδt AA' = OAδθ = OAΩδt = IωΩδt Newton's second law states that torque = rate of change of precession, ∴AA' / δt = T ∴T = IΩω