Motion
- the process of changing position
Describing Position

Reference point – the starting point you
choose to describe the location, or
position, of an object

Position – describes an object’s distance
and direction from a reference point

Displacement – the difference between
the starting position and the final position
Speed

the distance an object moves in a unit of time
◦ ex. 2m/s or 60 km/h

Constant Speed
◦ when an object moves the same distance over a
given unit of time

Changing Speed
◦ when the distance an object covers increases or
decreases over a given unit of time
Average Speed

total distance traveled divided by the
total time
speed(s) = distance(d)/time(t)
Calculating Speed (s = d/t)
1.
On a hike you travel 2800 m in 2 h.
What is your average speed?
2.
A jet airliner flew 4100 km from New
York City to San Francisco in 4.25 h.
What was its average speed?
3.
How long would it take you to bike 20
km at an average speed of 5 km/h?
Velocity

the speed and the direction of a moving
object
◦ ex. 5 m/s to the east

Constant Velocity
◦ An object moves with constant speed and its
direction does not change
Changing Velocity

Velocity changes if either the speed or the
direction of the object changes
Acceleration

the measure of the change in velocity
during a period of time
◦ Positive Acceleration
 acceleration is in the same direction as its motion;
speeds up
◦ Negative Acceleration (deceleration)
 acceleration is in the opposite direction of its
motion; slows down
DESCRIBING MOTION WITH
GRAPHS
DISTANCE- TIME GRAPHS

A graph that shows how distance and time
are related.
◦ Time is on the x axis
◦ Distance is on the y-axis
 shows the distance an object travels from a reference
point.

This type of graph shows how an object’ s
position changes over time
DISTANCE- TIME GRAPHS

The line on this distance-time graph shows
that the bus is traveling at a constant speed
DISTANCE- TIME GRAPHS

The line on this distance-time graph shows
that the object’s speed is changing
DISTANCE- TIME GRAPHS

Distance-Time graphs can be used to
compare the motion of two objects
◦ The slope of Line A is greater than the slope of
Line B. The object A traveled faster than the
object B
SPEED- TIME GRAPHS

Shows the speed of an object on the y-axis
and time on the x-axis.
◦ It shows how the speed of an object changes
during an interval of time.
Constant speed
Acceleration