This question doesn’t make sense to me: the question is, describe what happens to the water molecule in figure one (the one in the picture)

what was the acceleration of the 2 kg cart?

⇒ 16.0 cm/s2

what was the acceleration of the 4 kg cart?

⇒ 8.1 cm/s2

what was the acceleration of the 6 kg cart?

⇒ 5.3 cm/s2

54 degrees incident angle = reflected angle

angle is from normal turned to line of ray