The string connecting P and Q suddenly breaks after 3 s while force F is still being applied.
Learners draw the velocity-time graph for the motion of P and Q before and after the string breaks, as shown below.
Write down the time at which the string breaks. Justify your answer. (3)
Which portion (X, Y or Z) of the graph represents the motion of box Q, after the string breaks? Use the information in the graph to fully support the answer. (4)