The potential energy of a particle of mass \( 4 \, \text{kg} \) in motion along the \( x \)-axis is given by \( U = 4(1 - \cos 4x) \, \text{J} \). The time period of the particle for small oscillation \( (\sin \theta \simeq \theta) \) is \( \left( \dfrac{\pi}{K} \right) \, \text{s} \). The value of \( K \) is __________.
