A. Recognizing Motion
1. An object is in motion when its
distance from another object is changing.
2. Movement is based upon ones point of view based on a reference
We assume reference points are stationary.
b. A reference point is a place or object used for comparison to
determine if something is in motion.
c. An object is in motion if it changes position relative to a reference point.
1. In science we use the International System of Units (SI) and is based on units
The basic SI unit of length is a meter (m).
b. cm = centimeter: 1/100 of a meter
c. mm = millimeter:
1/1000 of a meter
km = kilometer: 1000 meters
C. Calculating Speed
1. Speed is a
type of rate.
The speed of an object is the distance the object travels per unit of time.
3. Formula: Speed = Distance
When the speed of an object does not change, it is known as Constant Speed.
5. Constant speed is difficult to
maintain. (bike, car, running, walking)
6. Average speed (most common) is calculated when constant speeds
are not or can not be maintained.
1. When you know both the speed and
direction of an object’s motion, you know the velocity of the object.
2. Speed in a given direction is called
E. Graphing Motion
1. A motion graph indicates time (x-axis) and
is the rate at which velocity changes.
Velocity has 2 components: speed and direction.
2. Acceleration changes if
a. speed increases
speed decreases (sometimes deceleration, or negative acceleration)
c. direction changes.
3. To determine the acceleration of an object, you must calculate the change in velocity during a
unit of time.
a. If velocity is
measured in meters / second and time is measured in seconds, the unit of acceleration is meters per second per second.
b. This unit is written as m/s². (meters per second squared)
4. To calculate the acceleration, subtract
the initial velocity from the final velocity and divide that by the elapsed time.
(Final velocity – initial velocity) (Vf – Vi)
----------------------------------- = --------- = Acceleration
(Final time - initial time) (tf – ti)