Answer the following in brief:
 
Why is straight-line motion called one-dimensional motion, whereas motion in a plane is called two-dimensional motion? Explain by comparing the two.
 
Straight-line Motion Motion in a Plane
The object moves along a . The object moves in  on a flat surface.
It is because only one coordinate is needed to describe its position. It is because two coordinates are required to describe its position.
The throughout the motion. The  during the motion.