The diagram shows a strobe photograph of a mark on a trolley X, moving from right to left, in
collision with another trolley Y which had no mark on it.
After the collision both trolleys are in motion together.
Which one of the following is consistent with the photograph?
A Trolley Y has the same mass as trolley X and was initially stationary
B Trolley Y had a smaller mass than X and was moving from right to left
C Trolley Y had the same mass and was initially moving left to right at the same speed as
trolley X
D Trolley Y had the same mass and was initially moving left to right at a higher speed than
trolley X