The displacement of a block attached to a horizontal spring whose spring constant is 9 N/m is given by x=0.4cos(2.2t0.8) m. The block is of mass kg. The total energy of the system is J. What is the earliest time (t>0) when the kinetic energy equals one-half the potential energy? s. The acceleration of the block at t = 2.3s is m/s2.