An object with mass 0.150kg is acted on by an elastic restoring force with force constant 10.7n/m . the object is set into oscillation with an initial potential energy of 0.150j and an initial kinetic energy of 6.70? 10? 2j . what is the amplitude of oscillation? what is the potential energy when the displacement is one-half the amplitude? at what displacement are the kinetic and potential energies equal? what is the value of the phase angle \phi if the initial velocity is positive and the initial displacement is negative?