A wooden block of mass 2kg is kept on a smooth horizontal ice surface. Two students pull the block by tying ropes to it.
(i) Student A pulls with a horizontal force of 15N towards the east, while Student B pulls with an equal horizontal force of 15N towards the west. Identify the nature of the forces acting on the block in this situation and state the value of the net force.
(ii) Explain whether the state of motion of the block will change under the conditions given in part (i). Give a reason for your answer.
(iii) Suppose Student B suddenly lets go of the rope while Student A continues to pull with 15N eastward. Explain qualitatively how the motion of the block will now change compared with its motion in part (i).