An apparatus similar to the one used in lab uses an oscillating motor at one end to vibrate a long rope with frequency f = 40 hz and amplitude a = 0.25 m. the rope is held at constant tension by hanging a mass on the other end. the rope has mass denstiy μ = 0.02 kg/m, and tension t = 20.48 n. assume that at t = 0 the end of the rope at x = 0 has zero y-displacement and is moving downward. what is the y-displacement of the piece of rope at x1 = 0.5 m when t = 0? y1 =