Motion 1-1, 1-2 Key Terms

Theory of Plate Tectonics

The theory that pieces of Earth's outer layer are in constant motion

Instantaneous speed

the speed of an object at one instant of time

reference point

A place or object used for comparison to determine if an object is in motion

International system of Units

A system of measurement based on multiples of ten and on established measures of mass, length, and time.

plates

Large pieces of earths crust that move due to convection currents.

Velocity

Speed in a given direction

Meter

The basic SI unit of length.

speed

The distance an object travels per unit of time

average speed

The overall rate of speed at which an object moves; calculated by dividing the total distance an object travels by the total time.

slope

The steepness of a line on a graph

motion

When one object's distance from another is changing.