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\begin{aligned} \Delta \omega &=250 \dfrac{\mathrm{rev}}{\mathrm{min}} \cdot \dfrac{2 \pi \mathrm{rad}}{\mathrm{rev}} \cdot \dfrac{1 \mathrm{~min}}{60 \mathrm{~s}} \\  &=26.2 \, \dfrac{\mathrm{rad}}{\mathrm{s}}.\end{aligned}