Science P6 NHPS 2018 SA1 Q20

Andy carried out the experiment below. He rolled the iron ball down the wooden plank and recorded the time taken for the ball to travel from A to M and from M to V before and after object X was placed below the wooden plant as shown below. The results were then recorded in the table below.
Time taken to travel from A to M (s)Time taken to travel from M to V (s)
Without object X1526
With object X1134
Which of the following is/are possible explanation(s) for the difference in the time taken for the ball to travel from one point to another point?(You may select more than one answer)