2. Frames of ReferenceFrames of Reference
 Object or point from which motion isObject or point from which motion is
determineddetermined
 Most common is theMost common is the
EarthEarth
 Motion is a changeMotion is a change
inin positionposition relativerelative toto
a frame of referencea frame of reference

3. What is motion?What is motion?
 If you are standing in one place, and your friendIf you are standing in one place, and your friend
walks by you.walks by you.
 Are you moving relative to your friend?Are you moving relative to your friend?
 Is your friend moving relative to you?Is your friend moving relative to you?
 Are either of you moving relative to the earth?Are either of you moving relative to the earth?

4. Answer:Answer:
 You are moving relative to your friend, andYou are moving relative to your friend, and
your friend is moving relative to you!your friend is moving relative to you!
 You are not moving relative to the earth,You are not moving relative to the earth,
but your friend is. You are both movingbut your friend is. You are both moving
relative to the sun!relative to the sun!

5. What is motion?What is motion?
 If you and your friend are walking down the hallIf you and your friend are walking down the hall
together at the same speed, in the same directiontogether at the same speed, in the same direction
 Are you moving relative to your friend?Are you moving relative to your friend?
 Is your friend moving relative to you?Is your friend moving relative to you?
 Are either of you moving relative to the Earth?Are either of you moving relative to the Earth?

6. Answer:Answer:
 You are NOT moving relative to yourYou are NOT moving relative to your
friend, and your friend is NOT movingfriend, and your friend is NOT moving
relative to you. You both are movingrelative to you. You both are moving
relative to the earth.relative to the earth.

7. Explanation
 Distance is the actual length measured
of a particular path taken.
 Displacement is the length and
direction of a straight line drawn from
the start to finish.

8. Evaluation
Distance vs. Displacement HO 1.5

9. Explanation
What’s your Vector?
 The most important distinction between
“distance” and “displacement” is that distance is
a scalar and displacement is a vector.
 Scalars are simple magnitudes.
 15 apples
 135 miles
 Vectors contain information about the magnitude
(size) and direction of a physical observable.
 64 miles Southwest
 Vectors are typically depicted as arrows drawn
with a specific length and pointing in a specific
direction.

10. your
home
your
school
A displacement has
Size = length
of this arrow
displacement from
home to school
displacement from
home to school
2 Displacement and
distance
To go to school from home...
size & direction.

11. Distance = length of path
you travelled
(≠ size of displacement)
l1l2
l3
2 Displacement and
distance
To go to school from home...
your
home
your
school
= l1 + l2 + l3

12. Elaboration
What’s your Vector?
 A car travels 6 miles East and then 8 miles North.
 Determine the distance traveled by the car.
 Draw and describe the displacement vector of the car.
6 mi E
8 mi N
10mi
53o
N of E
So the car’s
displacement is 10
miles NE

13. Conclusion
Summary of Concepts
 Distance is the length of the path traveled.
 Displacement (from “dis”-place to “dat”-place)
is the length and direction of a line from start
to finish.
 Motion is a change in position relative to a
point of reference.
 Distance is a scalar quantity that contains only
magnitude
 Displacement is a vector quantity that
contains both magnitude and direction.

14. total distance = ?
total displacement = ?
3km + 4km = 7 km
total distance
total displacement
3km north + 4km north
= 7 km north
N
4 km
7 km
north
3 km
Adding displacements
A car travels 4 km northA car travels 4 km north then 3 km north.

15. 4 Adding displacements
A car travels 4 km northA car travels 4 km north then 3 km south.
4 km
1 km
north
3 km
total distance = ?
total displacement = ?
= 3km + 4km = 7 km
total distance
total displacement
= −3km south + 4km north
= 1 km north
N
a Graphical method

16. 4 Adding displacements
A car travels 4 km northA car travels 4 km north then 3 km east.
4 km
3 km
φ 5 km
total distance = ?
total displacement = ?
= 3km + 4km = 7 km
total distance
total displacement
N
a Graphical method
d2
= 32
+ 42
d =5 km NE

17. ‘tip’ of p joined to ‘tail’ of q
p
q
p + q
Tip-to-tail method:
Graphing