Right !..

Why so ?.. because when  is falling into the well, it gains velocity, so, during this time it moves faster and get ahead of the others. By similar reasons  looses the velocity while climbing the hill and get delayed.
 

N.B. We should consider not the absolute value of velocity, but the component parallel to the X-axis. Actually, this does not change the answer:  consider forces acting on . It is the reaction N that is responsible for accelerating of the ball in the horizontal direction.
 


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