As a pre-med student preparing to take your MCAT, you want to ensure you have a solid foundation in Translational motion for the physical sciences section, not just in terms of how to solve equations and apply formulas, but also a conceptual understanding of the information.
Depending on the type of physics course you took in college, you would have learned how to solve translational motion questions in 1, 2, or 3 dimensions. Yet for the MCAT you only have to worry about solving kinematics questions in 1 or two dimensions, or sometimes a combination of the two.
Understanding the nature of these dimensions will be the first step in mastering MCAT physics. The concept of 'one dimension' refers to motion occurring in a single direction. The direction can face any which way but will never veer off course.
Common single dimension problems in MCAT physics will refer to motion happening in the x-direction, or in the y-direction.
Just because the two are oriented 90 degrees from each other, does not change they fact that they each represent a single direction.
In fact, you can even break from tradition in terms of what you call your 'x' or 'y' direction. The traditional graph you learned in school had you draw a line parallel to the horizontal as the x-direction, and other line perpendicular to the horizontal or parallel to the vertical as your y-direction.
And while this is still the case, you don't have to stick with this if you don't want to. You may choose to label your horizontal as 'y' and your vertical as 'x', as long as you are consistent with the associated math equations and appropriate units.
But let's not forget our two-dimensional questions. If you have a line represented on a graph, somewhere between the x and y components, this is said to occur in 2 dimensions, because we're not focusing on both the x-portion and y-portion of this line.