= Solution
Let $I_\perp$ denote the <moment of inertia> normal to the disc and $I_d$ that about any central diameter. <Rotational symmetry> makes the two perpendicular diameter values equal. By the <perpendicular axis theorem>, $I_\perp=2I_d$. The intended <angular impulse> has magnitude $J=I_\perp\omega_0$; delivering that magnitude about a diameter instead gives $J=I_d\omega$. Thus
$$
I_d\omega=2I_d\omega_0,\qquad\boxed{\omega=2\omega_0.}
$$
These are <principal axes>, so <angular momentum> is parallel to <angular velocity> in both cases. Equal delivered <angular impulse> means equal magnitude of the change in <angular momentum>, not equal rotational <kinetic energy>; the actual rotational <kinetic energy> is twice the intended value.
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