(c) A wave is travelling along a string. The string can be modelled as a single line of particles and each particle executes simple harmonic motion. The period of oscillation of the particles is 0.80 s. The graph shows the displacement y of part of the string at time t= 0. The distance along the string is d. , .' 6 , , J -' C111 direction of travel of the wave (I m ()1 5_I (i) On the graph, draw an arrow to show the direction of motion of particle P at the point marked on the string. (1) (iii) Show that the speed of the wave is 5.0 m S4. (3) (iv) On the graph above, label with the letter X the position of particle P at t= 0.40 s. (1) (Total 15 marks)