Final answer:
A rigid motion is a transformation that changes the position or orientation of a figure without altering its shape and size, including rotations, reflections, and translations.
Step-by-step explanation:
When we talk about a transformation being a rigid motion, we mean that the transformation moves a figure in such a way that the shape and size of the figure do not change. Rigid motions include rotations, reflections, and translations. For example, rotating a shape around a fixed point, flipping it over a line, or sliding it to a new position without altering its size or shape are all types of rigid motions in geometry. These motions are referred to as 'rigid' because the object in question remains exactly the same in terms of its dimensions and internal properties; only its position or orientation changes. The concept of rigid motion is crucial when studying the kinematics of objects because it allows us to analyze the movement or positioning of objects without accounting for deformations.