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Name: -----------
Unit -2
Date: _ 10/3 __ Period: ------
Distance vs. Displacement
Essential Questions:
• Why do we need 2 concepts for "how far" - distance vs.
displacement?
• How do we "measure" motion to communicate about it2
Questi-ons we ask about motion
• Where did the object start moving?
• When did the object start moving?
• How far did the object travel?
• How fast was the object moving?
• In what direction was the object moving?
~ Was the object speeding up or slowing down?
The motion equations help to answer these' questions &
make
predictions about motion
Formulas d
Average Speed = .6.t
!'iv Average Accderation = !'it
Average Velocity = ~" - et
vi + vf Average Velocity = ~-~
2
r - , ---,.Slide 2
1 ~·
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O_bjectives
.. Explain the Greek symbol "delta" or~ This symbol appears a
lot in physics and mathl
• Define dist~nce
• Define-displacement
• Explain the difference between a scalar vs. v~ctor -which
is-distance and which is displacement-'?
Review: What is Hposition"?
" Position or "x" is the location of the object on a coordinate
systems ( or "number line").
Os ls 2s
0 Question: What is th~osition of the runner at.Os? Vm
., Question: What is the position of the runner at 2s?
S-0/Yl
sliae3
Slide4
2 ~·
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What is "delta" or~?
" ~ means '-'subtraction"
• What are you subtracting? - -It depeuds .Qn the variable
after~: _
Formulas d
Average Speed= Lit
c'.', v A1,erage Acceleration = .:"It
A v·1· L'i.X , 1-..vernge e oc1ty = L'i..t
~t means "subtract two time ·instants"
Llx means "subtract two positions"
~v means "subtract two velocities"
v- = v-+ ~ t t ' -
Ayerage Velocity = V; + ""ir 2
Slide 5
A Tens you to subtract "initial" and ''finarJ values· 0 ~ means
subtraction of
"end value" - "start value"
.. "end value" is called "final" or "f' e.g., x1 means "final
position"
" "start value" is called "initial" or "i" e.g. , xi means
"initial position"
Note: Initial means "start" NOT your name initials!
Slide6
3
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~ Tells you to subtract Hinitial" and Hfina!" vaJues
• !J.. means subtraction of "initial value" - "final "9ffle"
Today we will focus on 6.x
• What values are you subtracting? It depends on the variable
after ~:
.At means "subtract two time instants"
!J..x means "subtract two positions"
.ti v means "subtract two velocities"
Distance vs. Disp~acement
.. Distance is the total length of your actual path Symbol:
"d"
., Displacement is the straight path from start to finish
Symbol: "!J..x" Math definition: 11,1: = x 1 - xi Conceptual
Example:
d is the actual path you took.
L1x is the displacement - straight path from initial position to
final position
Slide 7
Slide8
4
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Practice 1
Frank walks from x1 to x2
a)What is the distanced he travels? __
1/,____D;_.n-J------=---
b) What is· his displacement fix? tix = x2 - x1 = -20m -
(25"rrij
~ -45"m \
clire,.of,
----t--f---+---t----i------il,llill--+---+--+-----!, ___
.....__, X (m) -20 -10 0 10 20
Practice 2
Frank then walks from x2 to x3.
a)What is the distanced he travels? 25' rYJ b )What is his
displacement ll.x?
30
Slide 9
.6x = X3 - X2 = sty) - (- z o JY1) = s rvr -t -zo/11 = 25""
I">)
~-7 . ............. :....-----'~---'----r .....
;,_=~-=-=~--===·==
-- I I I I ' ---1 x(m) -20 -10 0 10 20 30
Slide 10
~-tu~ (!)r"'
a.n--J.oU41& ,-
Di rco(\..o"' (/.1 1'? ~ n'#
Ma~ '-fuOfl. (,.,d
2S:P1
5
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Practice 3
Consider Frank's total trip from x1 to x3.
a)What is1he distanced hetra-vels? '/~I"? + 2 S-PJ b)What is his
clisplacement Ax? ~ rO'>,
""ac X3 ~xi~ 5' WI - (2s /o/1) = i 3 D;r,) ,r.c; f'lvz.. /"Y7
Ct.~ ,· ~
X2 X3 /
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Practke 3
Draw the displacement of Frank's total trip from x1 to x3 as an
arrow that points from start to finish:
X2 X3 LlXtrJr X1 ~ It
' - I I .. r ' -20 -10 0 10 20 30 All vectors are drawn as
arrows to show the direction.
Displacement is an example of a vector!
Practice 3 - Ans'1ver
1 X (m)
Slide 13
Draw the displacement of Frank's total trip from x 1 to x3 as an
arrow that points from start to finish: }"\.. c. . ,;d ,..
CX j,-~ °"'t:,~ ~~ ,rivf:/' I __ _ X2 · X3 -20 m X 1 ..,_ ,;
,,,. "' ~"""""-===-==--"""""=a"""""' _______ """
----i---+-+----+----+-----ii,ffl-. --+-1-----+--l,~-. .-+I X (m)
-20 -10 0 10 20 30
Displacement is an example of a vector!
Every kind of vector has a magnitude (how much) and direction
(where):
Example: -20 m is a displacement with a magnitude of 20m and a
negative direction (to the left).
Slide 14
7
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Exit Ticket
Trish, Mike, and Juan-leave the park to go to a pizza shop.
Trish takes path A, J~n takes path B, and ~ takes path C.
Mi)G(._
Jua:4\
1. Who travels the longest distanced? _A _____ _ 2. Who has the
largest displacement Ill..? SQft-1