A pulley of radius \( 1.5 \, \text{m} \) is rotated about its axis by a force \( F = (12t - 3t^{2}) \, \text{N} \) applied tangentially (while \( t \) is measured in seconds). If moment of inertia of the pulley about its axis of rotation is \( 4.5 \, \text{kg m}^{2} \), the number of rotations made by the pulley before its direction of motion is reversed, will be \( {K}/{\pi} \). The value of \( K \) is _______.
