Define motion as being relative. Elicit how even when not moving, motion is relative to something. This may be the Earth's surface, or road, or the Sun. Define that an object is moving if its position relative to a fixed point is changing. Speed is relative to the Earth's surface. Elicit the definition of speed in terms of distance and time. Discuss instantaneous speed and average speed. Define speed as distance/time and discover that instantaneous speed will change momentarily.