Difficult# Rotating Wheel

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A uniform wheel rotates about a stationary axis, which passes through its center and is perpendicular to the plane of the wheel. Point A on the rim of the wheel sweeps an angle $\theta$ that changes with time $t$ as $\theta = b \cdot t$. Here, $b = 2.5 \space rad/s$ is a constant. Find the radial acceleration of point A at the moment its linear velocity is $1.4 \space m/s$.