Physics
Motion, Speed, and
Velocity
SC Standards Covered
PS-5.1
Explain the relationship among distance, time,
direction, and the velocity of an object
PS – 5.2
Use the formula v=d/t to solve problems related to
average speed or velocity
PS – 5.6
Represent linear motion of objects on distance –
time graphs
Motion
• When an object changes its position,
motion has occurred.
– Distance- How far an object has moved.
– Displacement- How far an object has moved in
relation to its starting point.
– Consider direction
Example: Two runners travel along the same
straight path in a straight line for 500 meters.
At the end of the run their distances are the
same but their displacements are different.
How can this be so?
Speed- Distance an object
travels per unit of time
Relationships between speed, distance, and
time:
Speed = Distance/ Time = d/ t
» Constant Speed- speed does not change
over time
» Average Speed- speed of motion when
speed is changing
Avg Speed = Total Distance/ Total Time
» Instantaneous Speed- speed at any given
moment in time (speedometer)
Graphing Motion
• Graph
distance
on the yaxis and
time on the
x-axis
Slope = rise = distance = speed
run
time
Distance - Time Graph
• If something is not
moving, a horizontal
line is drawn.
• If something starts out
slow and then speeds
up, its change in
speed can look like
this.
Learning Checkpoint
This graph shows several
stages of motion:
•Stage 1: 100 m in 10 s
•Stage 2: 50 m in 10 s
•Stage 3: 150 m in 20 s
Calculate the speed as indicated by
each of the colors.
Calculate the average speed.
What is the total distance?
What is the displacement?
Solution
Stage 1: S= d/ t
100 m/ 10 s= 10 m/s
Stage 2: S= d/t
50 m/ 10 s= 5 m/s
Stage 3: S= d/t
150 m/ 20 s= 7.5 m/s
Ave Speed= Tot d/ Tot t
300 m/ 40 s= 7.5 m/s
Distance = 300 meters
Displacement = 0 meters
Velocity
• The speed and direction of an object’s
motion.
– 88 km / hr southwest