Lesson 1: Describing Motion

Frame of Reference (Reference Point)

An arbitrary system to which an object is compared to describe its motion.

Motion Diagram

A figure showing he position of a moving object at equal time intervals.

In a particle model…

you replace each object under study with a single point.

A coordinate system…

gives the location of the zero point of the variable you are studying and the direction in which the values of the variable increase.

Origin

The point at which all values in a coordinate system have the value zero.

Position

The distance and direction from the origin to the object.

Distance

The entire length of an object’s path, even if the object moves in many directions.

Magnitude

Size

Vector

A quantity with both magnitude and direction.

Scalar

A quantity that is just a number without any direction.

Time Interval

The difference between two times.

Time Interval

The time interval is equal to the change in time from the initial time to the final time.

Four Vectors Used in Physics

Velocity, Acceleration, Momentum, and Position

Displacement

A change in position.

Resultant

A vector that represents the sum of two other vectors.