ERMU STETTIN
COURSE CONTENT PHYSICS
Chapter 2 describing motion
Content
Concept knowledge ................................................................................................................................ 2
Classification of variables in physics ....................................................................................................... 3
A world build with particles ................................................................................................................ 3
To observe is to influence ................................................................................................................... 3
Sensory observation ........................................................................................................................... 4
Measuring properties at a certain moment ........................................................................................ 6
Relationships between variables ........................................................................................................ 7
The change of properties through time is governed by a universal law ............................................ 8
Variables that describe interactions over time .................................................................................. 9
Observing and studying motion ........................................................................................................... 10
The quest for a conceptual language in physics education. ................................................................ 11
Content knowledge describing motion dynamics .............................................................................. 18
The CBR motion detector from Texas Instruments ............................................................................. 23
Content knowledge describing motion kinematics ............................................................................ 24
The solution of content issues Chapter 2 Conceptual Integrated Science .......................................... 24
Preconcepts .......................................................................................................................................... 25
Phet simulations as a tool to test your conceptual understanding of linear motion. ......................... 26
1/29
Concept knowledge
Clicker test force (see Toledo)
Concept practical (light a bulb with a battery and a wire, also see Toledo)
→ concepts are hard to grasp, differences exist between the intuitive and scientific interpretation
of a concept, scientific concepts are difficult to apply in reality
= worldwide problem
= studied in educational research
→ knowledge of preconcepts and misconcepts
→ innovative methodologies: inquiry based, ict supported, hands on, cooperative learning, ….
Despite of many efforts, the concept shift from intuitive to scientific interpretation remains
extremely difficult.
Why?
The basic ideas in science are easy to understand. The way we pack these ideas and present them to
learners on the contrary are extremely cryptic. We present them as isolated concepts (↔
classification). We work within models (↔ reality). We use an abstract language of formulas and
definitions, math (↔common language, visualization, sensory information). This course aims to
introduce a science didactics that introduces scientific ideas and concepts starting from real
contexts, using common language, sensory observation, from a general to a detailed description,
similar to the way we naturally learn.
2/29
Classification of variables in physics
A world build with particles
In the same way that a house is built with bricks, a LEGO house is built with LEGO blocks, a puzzle
with pieces, a sentence with words, we and the world that we live in is built with building blocks
called ‘particles’. Apparently, a set of 12 particles is sufficient to build the entire world . they are
called
To observe is to influence
Humans experience the world, observe their surroundings and try to make sense of the
observations. These observations give a snapshot of the surroundings and information concerning
the properties of these surroundings at a specific moment. Observations over time provide us with
information about changes of the properties of our surroundings. Especially this information about
changes is vital in the survival of living beings.
By observing the world, humans influence it. This influence is called the forces the person exerts
upon his surroundings . Influence works two ways. The person and his surroundings influence each
other. The influence of the surroundings on a person are called the forces exerted by the
surroundings upon the person. In symbols:


Fsurroundings / person en Fperson/ surroundings
Also objects/ substances influence each other. Objects/substances exert forces upon their
surroundings and the surroundings exert forces upon objects/substances. In symbols:

Fobject / surroundings
and

Fs surroundings / object
(Example falling ball, rubbed balloons, magnet and nail)
In common language we refer to forces as ‘pushing and
pulling’. To visualize the influence, we draw an arrow.
3/29
Try to visualize the force you exert upon the given object in the following situations:
You push a car/ You lift a bucket/ you hold a book/ you sit on a chair / you swim/ you jump upward
In nature, 4 fundamental influences appear to exist. At that level, we call them interactions: the
interaction between objects and substances with mass, the interaction between objects/ substances
with charge, the interaction between particles within the nucleus of an atom: protons and neutrons
and interactions between the building blocks of these particles: quarks.
Interactions always cause a change of properties. Sometimes these changes are so small or so slow
that they cannot be observed macroscopically. When you look at an object for example, this object
was influenced by light and inevitably was disturbed. This disturbance is so small that you cannot
observe a change in the properties of the object while you are looking at it. Sometimes the
disturbances can be observed. When you touch a snowball for instance, it starts to melt.
Sensory observation
In order to observe, humans naturally observe the surroundings using their senses.
We poses 5 senses: we see, feel, smell, taste and hear the world. Fundamentally these interactions
take place between charged particles (electromagnetic interactions) and between masses
(gravitational interaction).
With the information gathered from his observations, a person gains information about the
properties of objects and substances.
See: in order to see an object/ substance, light that interacted with this object / substance
must reach your eye. Light is a kind of electromagnetic disturbance that progresses . This
disturbance is generated by the relocation of an electron in an atom. This disturbance is
detected when it interacts with your optical nerves. The electromagnetic disturbance that it
triggers, is interpreted by our brain and translated into optical information concerning the
object/ substance. To communicate this information we use words as : color, how tall,
volume, position, height, mobility, viscosity, … .
o
color : overall information about the wavelengths of detected light
4/29
red
bleu
o
Position, how high, distance to, shape, volume: the direction of the incoming and
the angle between the incoming light for both eyes.
o
Mobility: how quickly is the position changing?
o
Viscosity: how quickly is the shape of the object / substance changing?
Smelling: in order to smell an object/ substance small molecules originating from the object,
must reach your nose and interact with the sense of odor in your nose. The electromagnetic
disturbance that it triggers, is interpreted by our brain and translated into odor information.
Tasting: in order to taste an object/ substance molecules originating from the object/
substance, must reach your tongue and interact with the senses of taste in your tongue. The
electromagnetic disturbance that it triggers, is interpreted by our brain and translated into
information which we call taste.
Feeling: in order to feel an object/ substance, you mast touch it with your skin and interact
with the sense of touch . The electromagnetic disturbance that it triggers, is interpreted by
our brain and translated into information which we call:
o
o
hardness/ softness
shape
5/29
o compressibility
o weight
o how warm/ how cold it feels
Hearing: in order to hear an object, a pressure wave generated by the object must be
transported through the air, reach your ear and interact with your sense of hearing. The
electromagnetic disturbance that it triggers, is interpreted by our brain and translated into
information which we call sound, noise, music, … .
Sensory information has a limited accuracy and precision and is determined by a place and a
moment. Sensory information is also subjective as it is the result of personal interpretation.
Based on the information we obtain by sensory observation, our understanding of the world around
us becomes more detailed. We succeed in categorizing objects and substances into metals, liquids,
soft, …. .
Measuring properties at a certain moment
In order to obtain a more detailed picture of the world, sensory information is supplemented with
measurements. Measuring instruments are similar to senses, measuring instruments interact with
their surroundings. Similar to sensory interactions, these interactions are fundamentally
electromagnetic and gravitational.
Information obtained from measurements is more detailed, more precise, more objective, but also
subjected to interpretation in our brain. We read data, interpret sound produced by measuring
devices … .
A property that is measured by a measuring instrument is called a variable. Examples of variables
are: time, temperature, mass, volume, position, charge, … . the result of a measurement is
expressed in a number and a unit.
smelling
tasting
hearing
taste
sound
How warm/ how cold
Electric charge
compressibility
formability
weight
Hardness/ softness
viscosity
mobility
How much space it
takes
Position
Height
shape
color
Sensory observation of properties → snapshot
seeing
feeling
odor
This extra information gives us a better understanding of the properties of the world surrounding us.
The snapshot of the world evolves from cloudy to clear. The following scheme shows a limited view
of the information obtained from measurements.
Measurement of properties →snapshot
6/29
…
Manometer
pressure
Indika-tor
pH meter
acidity
Thermometer
Voltmeter
Ampère-meter
Temperature
Current,
voltage
Elektroscoop
charge
Mass
Hardness
Balans
Measuring cup
Volume
Microscoop
shape
ruler
Position
Light
ruler sensor
prims
Length
Spectroscoop
waveleng
th
Clock
Time
…
Relationships between variables
Between some of the variables relationships exist. Some variables are related to each other.
For instance: there is a relationship between the mass of a liquid and its volume: the greater the
mass, the greater the volume. Moreover: when the mass doubles, the volume also doubles.
Relationships like this reveal hidden information about the properties of nature.
The previous example possibly gives us information
about the arrangement of the particles in a liquid.
Imagine we know that a liquid is built with small
particles. The relationship between mass and volume
might suggest that distance between particles is fixed. Doubling the mass, means doubling the
amount of particles. When the distance between particles is fixed, this would result in doubling the
volume.
This is a possible conclusion. More measurements would be necessary in order to be sure about the
conclusion.
The measurements give information about one specific aspect of the particle model. What about
the arrangement of particles in solids and gases? What about the mobility of particles?
Another example:
The mass of a moving object and its velocity both determine how difficult it is to stop it. Mass and
velocity appear to be related. This relationship is expressed by combining them in a new variable
which we call impulse.
The previous relationships give rise to the definition of new variables and are summarized in a
formula.
m
for instance stands for the relationship between mass and volume and is defined as density ρ.
V
7/29
More examples:
For an object with uniform motion on a straight track, its displacement is proportional to the
elapsed time. Their ratio is called average velocity v 
x
t
Electric resistance expresses the relationship between the electric voltage across a conductor and
R
the electric current through the conductor
U
I
…
The information gathered from measurements clarifies the microscopic meaning of variables. What
for instance is the meaning of the variable temperature? Measuring it with an analog thermometer,
relates temperature to the length of a liquid column. But what is the fundamental meaning of
temperature? When you put a drop of ink in some water, the ink diffuses in the water. Now change
the temperature of the water and repeat the experiment. You discover the following relationship:
the higher the temperature of the water, the higher the diffusion rate. This relationship alights the
nature of the concept temperature. Apparently the macroscopic concept of temperature is related
to the microscopic concept of particle speed: the higher the average speed of the particles, the
higher the temperature of the water.
The change of properties through time is governed by a universal law
Properties change through interaction, but apparently these changes are not random.
For instance: imagine you drop an object in vacuum. A relationships exists between the initial height
of the object and its velocity just before it reaches the ground.: mghstart 
1 2
mv eind .
2
Or apart from a small correction a relation exists between the height from which a person is falling
and the maximum length of the bungee that holds him: mghstart 
1 2
kx eind .
2
These relationships between properties before and after changes are more complex, not at first
sight clear. The formulas that express these relationships are more complicated. They point to a
deeper law in nature. This law governs all changes in nature. As far as we know this law has not been
violated. It is called the law of the conversation of energy.
The law poses that you can calculate a certain quantity for every object/ substance, which we call
‘the energy of the object/ substance’. Through the manifold changes that nature undergoes, the
total energy in the universe remains unchanged.
The energy of an object is determined by the properties of the object at a certain moment: the kind
of matter it is built of (chemical energy), the velocity of the object (kinetic energy), the velocity of
8/29
the particles that form the object (thermal energy) , the position of the object in relation to its
surroundings (potential energy): its position in relation to earth (gravitational potential energy), its
position in relation to charges (potential electromagnetic energy), its position in relation to a string
(elastic potential energy) … . In case you made measurements of velocity, position, mass,
temperature, … and you know the correct relationships, you can calculate the energy of the object
at that moment by adding up all different contributions.
If anything changes with the object, the context changes, variables change and its energy will
change.
This is a very abstract statement. It is a mathematical principle. To ever object you can connect a
quantity that changes according to a fixed law. You can calculate the total energy for a specific state
of the universe. Although the universe goes through many changes this total energy remains
unchanged.
Variables that describe interactions over time
Interactions cannot be observed, but the effects of the interactions can. Objects and substances
change shape, velocity and position, temperature and color , etc. . Some variables are defined to
describe the effect of these interactions over time:
Work: a variable that describes the change in position as a result of interactions
Power: a variable that describes the velocity at which the interaction is happening
Heat: a variable that describes the change in temperature as a result of interactions
….
9/29
Observing and studying motion
Assignment:
Observe and describe the following motions.
Describe the following motions by measuring.
Look for relationships between measuring results.
Present the results in a written paper using the scientific method.
Presents the results in an oral presentation.
Practical1: motion of an air bulb in an oil filled tube.
Practical2: motion of a falling object
Practical3:motion of a mass on a pendulum
Practical4: motion of a mass on a spring
Didactical remark:
Note that we start the study of the chapter by posing a number of research questions and performing
experiments. This methodology is called inductive. Learning starts from an offered real -life context and
experiences within this context. The methodology aims to engage the student to connect to the subject,
to give him experiences in different facets of the subject, to confront him with the personal preconcepts
he holds on the subject.
10/29
The quest for a conceptual language in physics education.
(BPS 2012, also see the ppt on Toledo: natural sciences 1 content/ materials chapter 2)
The physics didactics course focusses on the ways we communicate in physics. How do we
communicate, how effective do we communicate, how can we intensify class communication. Effective
communication is the prime condition that must be met in order to facilitate the transfer of scientific
knowledge.
Looking back I believe my personal focus on science communication was triggered when I myself
was a physics student. I remember the phrase, ‘what does this mean, what do you mean’ as the most
frequently used sentence amongst my fellow students during late night discussions. We had the
mathematical description, but ‘what did it mean’?
Later, when I was a very young teacher, during summer holidays, I prepared pupils that had failed
their physics examination. At the beginning of the first lesson I asked them ‘Tell me, what the
problem is, what is it that you don’t understand.’ They replayed: ‘I don’t understand anything about it’.
They had the abstract explanation, but failed to understand.
My students at the teacher training are all passionate about the subject. They chose to become
physics teachers. Their educational background is divers. Many of them start the course without a
good preparation in science or mathematics. But they share my passion for the subject and often
become great physics teachers. Largest part of class time is dedicated to discussion, translation of
abstract language into everyday language, the conceptual approach. Most time is invested in
answering the question ‘what does it mean and very much how shall I explain’.
Planet TWILO
To illustrate the problem I would like to use the story told by Leon
Lederman (The God particle). He tells the story of the inhabitants of
the planet Twilo. These intelligent extraterrestrial creatures, look like
humans, speak and act as we do, except for one thing: they are
unable to observe objects with a strong contrast between black and
white. Zebra’s for instance are invisible to them. When a Twilo delegation visits planet earth, they
are invited to the a football game. The Twillians are politely observing the game, enjoying the
atmosphere, but at first are completely unaware of the point of the game. It takes them quite some
time and close observation before they link the cheering of the crowds to a small deformation of the
goal net.
Non physicists are very similar to Twillians I believe. We as physicists allow them to join the game,
warmly invite them, show them what is happening, talk about it with passion, experiment,
demonstrate, we welcome them with open arms, but … we fail to make contact, fail to
communicate the point of the game.
Now I come to what I believe is the major quest we face in physics education and probably more
generally in science and technology education as a whole:
1. Language
When we communicate in physics we use a specific language. The abstract language of
formula’s, definitions, mathematics. This language has proven to be very effective. We can
11/29
communicate unambiguously, but it shows that only a small minority of people understands,
speaks the language of mathematics. For most pupils mathematics can be reproduced, for few
pupils mathematics is understood. As for the physicist the mathematical description of physical
concepts is clear he tends to minimalize the number of words he uses in explaining the concept.
Furthermore he tends to build his explanation of concepts on a numerous previously poorly
described and understood concepts.
2. Models
When we describe the world in physics we use models. These models are easy to describe using
mathematics. For instance when we describe motion that occurs in daily life, air friction is
neglected. This model of motion is easily mathematically described. For the nonmathematician the description opposes the information he obtains when he is moving through
the air, when he is observing motion in the air. The physics teacher is not only using the foreign
language mathematics, he is describing a world that is not the pupil’s world.
Moreover models often enlighten one fraction of the observable reality. For instance when we
describe a falling apple the physicist focusses on the apple and while in his thinking he includes
earth and air, he talks only about the gravitational force and silently neglects in the
mathematical description frictional forces, buoyance force. As a result the physics teacher
works with isolated concepts. He or she has no need for a classification of concepts. Pupils on
the other hand think in reality and need a lot of concepts. They ask themselves: what formula to
use? They do need a classification of concepts.
To summarize: physics teachers, who are specialists in using mathematics and describing the
physical world using simple models, are failing to translate their knowledge into a format that is
accessible to the layman in physics. We fail to connect.
In the following course a numerouws examples will be offered to illustrate this tendency of
minimalizing information in science class communication. The content of communication is
reduced to the minimum, sufficient for the scientist to comprehend but coded language to the nonscientist.
Many years ago I attended the Stephen Hawking lecture in Brussels at the VUB with my students. As
they were used to the conceptual approach I was a bit worried whether they would understand the
lecture content. The evening became memorable to them as we witnessed how Professor Hawking
broke down his language to analogies, drawings, ideas. He needed no formula’s. He made sure we
could grasp the idea, get a feeling about the meaning.
I strongly believe and experience in my everyday practice that we can communicate with every
pupil, given we adapt and open up our language. We do pay a price in precision in the message but
we gain in its accuracy.
Starting physics education using a conceptual approach: using every day language, within a context
taken from reality, fitting in a conceptual framework. Building on this conceptual fundament we can
refine, zoom.
I would propose the following sequence in the construction of physics education imbedded in an
inductive approach based upon experiences with scientific phenomena :
describing conceptually → understanding conceptually →explaining conceptually → describing
formally → understanding formally → explaining formally → calculating and predicting formally
12/29
Is it possible to explain physics concepts in a conceptual way? It indeed is not easy. Highly
experienced but theoretically educated physics teachers appear to experience great difficulties in
conceptualizing scientific descriptions.
Sometimes history can inspire us to construct the conceptual explanation. Going back to the 17th
century, Isaac Newton puts a great example of making crystal clear what he means by using certain
words.
(Great Experiments in Physics, First-hand Accounts from Galileo to Einstein, Morris H. Shamos,
p.46-p58)
The quantity of motion is the measure of the same, arising from the velocity and quantity of matter
conjunctly.
An impressed force is an action exerted upon a body, in order to change its state, either of rest, or of
moving uniformly forward in a right line. This force consists in the action only; and remains no longer in
the body, when the action is over. For a body maintains every new state it acquires, by its inertia only.
Impressed forces are of different origins; as from percussion, from pressure, from centripetal force.
Hitherto I have laid down the definition of such words as are less known, and explained the sense in
which I would have them to be understood in the following discourse. I do not define time, space, place
and motion, as being well known to all. Only I must observe, that the vulgar conceive those quantities
under no other notions but from the relation they bear to sensible objects. And thence arise certain
prejudices, for the removing of which, it will be convenient to distinguish them into absolute and
relative, true and apparent, mathematical and common.
More recent a different great example is set by Richard Feynman in his work ‘the Feynman lectures
on physics’ where a clear explanation of the energy concept can be found. From the Feynman’s
lectures, vol 1 4-1:
There is a certain quantity, which we call energy, that does not change in the manifold changes that
nature undergoes. That is a most abstract idea, because it is a mathematical principle. It says that there
is a numerical quantity which does not change when something happens.
13/29
The scientific method
The scientific method offers an effective methodology to scientifically study the world. It consists of
a number of steps which are described in the following scheme. Any experiments performed in the
following of the course have to be carried out following this scheme. In scientific reports the scheme
should be visible.
Problem
The problem is still very general. For instance: how is an air bulb moving in
a glass tube filled with oil? Why do I feel cold when I step out of the shower?
To solve this problem, many questions need to be answered. Is the
movement influenced by the way I hold the tube? How can I describe this
motion? Is the motion influenced by the kind of fluid I use to fill the tube?
Does it feel any different when the window is open? Am I also feeling cold
when I take a cold shower or when I step out of sea on a hot summers day?
Brainstorming
In a brainstorming a variety of ideas pupils have about the given problem
are summarized. Put no limitations to their imagination. Try and identify
as many parameters that are influencing the answer to the problem as
possible. As the result of the brainstorming pupils obtain a full
understanding of the context of the problem.
Research
question (RQ)
The brainstorming results in different research questions . A research
question is always phrased as follows: is there a relationship existing
between parameter A and parameter B?
For instance: is there a relationship between the time(parameter A) the air
bulb is moving and the distance (parameter B) it travels? Is there a
relationship between the initial temperature (parameter A) of water and the
pace (parameter B) in which it is cooling down?
Hypothesis
Pupils (even very young children) can give answers to research questions
and more over they can motivate these answers. These answers are
supported by experiences they had, information they extracted from what
they heard, read, saw on television.
Often the answers are not scientifically correct. The purpose of performing
the experiment is to check the scientific correctness of their theory.
Answers should be formulated both in words and in a graph. Often the
answer in words is more general as pupil’s observations of the world are
more general.
For instance: the longer the air bulb is traveling the more distance it will
cover. This answer does not clarify exactly how much more distance the air
bulb will cover: double the distance in double the time or four times the
distance in double the time?
14/29
In drawing the graph pupils are forced to make a clear statement about
their view on the answer. This assignment often puzzels them. They don’t
exactly know the answer, they have to make an assumption to the answer.
At this point the need for an experimental verification imposes itself.
Design of the
experiment
How is the experimental setup? How can we control parameters that are
influencing the answer to the research question? How can we measure the
parameters that we focus upon in the research question? How accurate is
the measurement? How can I improve the accuracy of the measurement?
In the experimental report the experimental design has to be made clear to
the level that it can be reproduced by another team. The setup can be
shown in a drawing or a picture.
Observations
While performing the experiment pupils are encouraged to observe and
take notes of these observations.
That way they critically reflect on the experimental setup and often change
and improve the setup.
That way they critically reflect on the accuracy and precision of their
measurements and will be able to weigh the reliability of their
measurements.
That way they are stimulated to become good observers, an important
capacity of scientists.
Measurements
Measurements are summarized in a table. The first column contains the
parameter that is controlled in the experimental setup: the independent
parameter. The second column contains the parameter the is measured in
function of the first, controlled parameter: the dependent parameter. For
instance: in the experiment with the air bulb pupils can decide to let the air
bulb travel for 3 seconds at a time (independent parameter, first column)
and the measure the distance (dependent parameter, second column) that
it covers.
Time(s)
0,0
3,0
6,0
9,0
12,0
15,0
Distance (cm)
0,0
2,4
3,8
6,1
7,6
10,4
About accuracy and precision:
The accuracy of a measurement system is the degree of closeness of
measurements of a quantity to that quantity's actual (true) value. The
15/29
precision of a measurement system, also called reproducibility or
repeatability, is the degree to which repeated measurements under
unchanged conditions show the same results.
A measurement system is considered valid if it is both accurate and
precise.
Graphs
On the horizontal axes the independent variable is displayed, on the
vertical axes the dependent variable.
For instance:
Motion of an airbulb in
a tube filled with oil
15
distance( 10
cm)
5
Series1
0
0
10
20
time(s)
The exel software is a handy tool to create graphs in no time.
Relationships
between
parameters
The graph offers a survey on the relationship between the measured
parameters. It shows a trend (linear, quadratic, inversely proportional…).
Individual measurements in the table don’t reveal this trend, they rather
reveal measurement errors. It is up to the experimenter to interpret the
graph and decide on a trend Once the trend is determined, the
measurements can be fit by a mathematical equation. The exel software
offers a tool that determines the best possible mathematical equation for a
chosen trend.
For instance:
16/29
airbulb in a tube filled
with oil
y = 0.6709x
R² = 0.9926
15
distance(
cm)
10
Series1
5
Linear
(Series1)
0
0
10
20
time(s)
The R2 value gives an estimate of the correlation between measurements
and of the precision of the measurement. The closer this value approaches
1, the closer the correlation between measurements and trend.
Reflection on
the hypothesis
After the interpretation of the measurement, the results are compared
with the hypothesis stated before the measurement. The results can
confirm the predicted relationship or can contradict it.
Scientific
explanation
In a final stage pupils try to make sense of the experimental results. They
try to fit the results into their own scientific framework and compare it
with the knowledge of the scientific community.
17/29
Content knowledge describing motion dynamics
See also manual Conceptual and integrated science Paul Hewitt, p. 19- p.40
Aristotle:
Natural motion: each object is build out of 4 elements (water, earth, air and fire). The natural place
of an object is linked to the predominant of its 4 elements. An object will naturally strive to move to
that place.
Violent motion: externally caused, imposed by pushes and pulls = forces.
Galileo Galilei: inertia
Each object is inert to change in motion. Naturally it maintains a constant linear speed. The change
in motion of an object is caused by an net external force. This net external force is the result of
unbalanced influences from the surroundings on the object.
→ Check yourself p. 22
Force:
Remember: also objects/ substances influence each other. Objects/substances exert forces upon
their surroundings and the surroundings exert forces upon objects/substances. In symbols:

Fobject / surroundings

Fs surroundings / object
and
In common language we refer to forces as ‘pushing and pulling’.
When a change in motion or a deformation of an object occurs, scientifically we say that a net force
is exerted upon that object .
When an object moves by constant speed on a linear track, we say that the net force exerted upon
that object is zero.
A change in motion occurs when the object starts to move, stops, slows down, accelerates or turns.
A deformation can also be considered as a change in motion on a smaller scale.
The net force is the total force exerted upon the object by its surroundings. It is the result of all
‘pushes’ and ‘pulls’ exerted upon the object.
The word ‘Force’ is synonymous to ‘interaction’. In every interaction, for every exerted force, two
objects are involved.
For instance in the following picture Mark and a box influence each other. Mark exerts a force upon
the box and the box exerts a force upon Mark.
To represent forces, arrows are used. For example the horizontal
force that Mark exerts upon the box is the right arrow. As the force is
exerted upon the box, it starts in the box. As the force works to the
right, the arrow points to the right.
The force the box exerts upon Mark is the left arrow in the picture. It starts in Mark and is pointed to
the left. Mark can feel how the box resists his push, how the box is pushing him back.
18/29
The direction of the arrow gives an idea of the direction of the push or pull. The length of the arrow
gives an idea of the strength of the push or pull.
A tiny push
A big push
A heavy push
In the following situation the horizontal pull Mark exerts upon the rope starts in the rope. You can
see in the following pictures that Mark is increasing the pulling force he exerts on the rope.
A conceptual notation
As a short notation for the force Mark exerts on the box we use:

FMarkontherope
Note that in this notation, in contrast with the notation for force you will find in most textbooks,
both objects that interact are included. By adding the index ‘Mark on the rope’ an essential aspect of
the concept force remains visible to the student.
If for instance in the case of the force earth exerts upon Mark, the

Fg
notation
would be used, the information that gravitational force is
the force that earth exerts upon Mark would be lost to the student.
A second advantage of the notation is that it is clear what person or
object we focus upon in the description. In this case focus lies upon
Mark.
Upon objects and organisms on planet earth two forces are always exerted, as objects interact with
the planet and with matter in its atmosphere:
o The pull -force of planet earth upon objects that have mass. This force is directed vertically
towards earth’s center.
o The pull force of air and other matter that is exerted upon objects. This force opposes
motion and is directed opposite to the direction of motion.
19/29
Methodology for drawing force diagrams of daily situations
Focus: start by focusing on the object for which you will draw the force diagram.
Observe: is the object stopping, starting, slowing down, accelerating or turning? When the answer is
yes, a net force must be working on the object. When the answer is no, the net force on the object
equals zero.
Chronology: an object falling → holding on object → an object with constant speed on a linear track
…. . Work from simple straightforward examples towards more complicated ones. Add a new force
in each example.
Using contexts in which the student is playing a part
Examples
Complete the following situations with the forces that are exerted upon the object. Make sure that
your force model is consistent with reality. Add in the drawing the surroundings that interacts with
the object.
-
Forces exerted upon a person falling from a tree / interaction between the falling person and
its surroundings
Do you observe starting, stopping,
slowing down, accelerating, turning?
Yes. The longer the person falls, the
higher his speed.
What can you decide about the net
force exerted on the person?
The net force isn’t zero. It is
directed vertically down.
Which forces act on the person?
The pulling force of earth on
the person vertically down.
The pushing force of the air on
the person vertically up. It is
smaller than the force of earth
on the person as the net force is
directed down.
20/29
-
A person falling down is hitting a trampoline. Draw a force diagram for the person.
Do you observe starting,
stopping, slowing down,
accelerating, turning?
Yes, the person is slowing
down.
Which forces act on the
person?
The pulling force of
earth on the person,
vertically down.
What can you decide
about the net force
exerted on the person?
The net force on the
person isn’t zero. It is
pointed vertically up as
the persons slows down.
The pushing force of the
air on the person
vertically up. It is smaller
than the force of earth on
the person.
The pushing force of the
trampoline on the person
vertically up.
The force of air on the
person and the force of
the trampoline on the
person combined, are
bigger than the force of
earth on the trampoline
as the person is slowing
down.
Assignment:
Do the following activities:
Catching a falling ball, picking up a chair, balancing a pound of sugar, pushing a table to give it a
constant linear speed, pushing a cupboard without it starting to move, walking with constant speed,
swinging a ball on a string in a circle, standing on a bathroom scale, pulling a magnet from the
blackboard,
For each activity draw a force diagram of all forces that act on the object. Identify influences and add

them in notation of forces: FAonB . Make sure you apply Galileo’s law of inertia.
Discuss your drawing with colleagues and possibly adjust it.
Scan the result of your work and upload it to Toledo.
More exercises:
- Forces exerted upon a person driving in linear motion with constant speed on her bicycle/
interaction of the cyclist and her surroundings.
- Forces exerted upon a person that has just landed on the floor/ interaction between the nail
and its surroundings
- Forces exerted upon a person on a bike slowing down/ interaction between the person and
its surroundings
21/29
-
Forces exerted upon the moon
→
Different forces: force of gravity, muscular force, support force, force of friction, magnetic force, net
force…
Mass: quantity of matter, measure of inertia
Weight: the force that an object exerts on its support!
Speed:
Equilibrium:
:
22/29
The CBR motion detector from Texas Instruments
See the manual on Toledo: CBR motion detector manual.
Didactical remark: The motion detector allows quick measurements of motion. Particularly
interesting is the measurement of human motion. This experiment allows pupils to feel what a
mathematical graph shows. The link between the abstract graph and the experience of constant
speed, acceleration, walking away, slowing down, being at rest … becomes more direct.
Ask pupils to walk relative to the motion detector in different ways. Ask the class to predict the
graph, perform the measurement and compare.
Results:
Walking away with constant speed
Coming back with constant speed
hypothesis
hypothesis
measurement
…
…
Walk away, slowing down
Walk away, speeding up
hypothesis
hypothesis
Measurement
…
…
Come back, slowing down
Come back, speeding up
hypothesis
hypothesis
…
Measurement
Measurement
Measurement
Measurement
…
Stand still
hypothesis
measurement
…
23/29
Offer pupils a methodology to read the graph. Check for different parts of the motion, the covered
track in a given time interval.
For instance in the give graph: in the beginning of
the motion only a small distance was covered in
the given time interval. Later in the motion more
distance was covered in the same time interval so
the object is speeding up. As time goes by, the
distance between the observer (located in the
origin) and the moving object becomes smaller so
the object is approaching the observer.
Content knowledge describing motion kinematics
Average speed:
Instantaneous speed:
Velocity:
Acceleration:
The solution of content issues Chapter 2 Conceptual Integrated Science
See for corrections also ‘solutions of exercises chapter 2’ on Toledo natural sciences 1, content,
lesson materials chapter 2
24/29
Preconcepts
From a young age and prior to any teaching and learning of formal science, children develop
meanings for many words used in science teaching and views of the world which relate to ideas
taught in science. Children’s ideas are usually strongly held, even if not well known to teachers, and
are often significantly different to views of scientists. These ideas are sensible and coherent views
from the children’s point of view, and they often remain uninfluenced or can be influenced in
unanticipated ways by science teaching. The previous general statements have been stated by
different theorists from Piaget (1929) onwards.
Children acquire these ideas prior to formal teaching in a very natural way. Young children, like
scientists, are curious about the world around them and in how and why things behave as they do.
Children naturally attempt to make sense of the world in which they live in terms of experiences,
their current knowledge and their use of language. It is these ideas that we call ‘childrens’s science’
(Osborne, 1980; Gilbert, Osborne and Fensham, 1982) It is the similarities and differences between
children’s science and scientist’s science that are of central importance in the teaching and learning
of science.
Research worldwide has revealed the following preconcepts on the concept of motion:
In children’s and pupil’s science







A motion with constant SPEED ≠ state of rest
Learners do not spontaneously connect displacement, time and speed. The concept of time
is no part of their thinking.
Objects accelerate instantaniously
Constant speed means moving constantly
Accelerate means catch up, overtake, pass
The instant objects catch up with each other they have the same speed
There is no clear difference between speed and acceleration.
Note the difference between children’s interpretation of concepts and the scientific interpretation.
In teaching the subject of motion the preconcepts held by pupils has to be taken into account.
25/29
Phet simulations as a tool to test your conceptual understanding of linear motion.
The simulations can be found on the internet following the link: http://phet.colorado.edu/
(reference: http://phet.colorado.edu/)
PhET provides fun, interactive, research-based simulations of physical phenomena for free. The
makers believe that the research-based approach- incorporating findings from prior research and
their own testing- enables students to make connections between real-life phenomena and the
underlying science, deepening their understanding and appreciation of the physical world.
To help students visually comprehend concepts, PhET simulations animate what is invisible to the
eye through the use of graphics and intuitive controls such as click-and-drag manipulation, sliders
and radio buttons. In order to further encourage quantitative exploration, the simulations also offer
measurement instruments including rulers, stop-watches, voltmeters and thermometers. As the
user manipulates these interactive tools, responses are immediately animated thus effectively
illustrating cause-and-effect relationships as well as multiple linked representations (motion of the
objects, graphs, number readouts, etc.)
To ensure educational effectiveness and usability, all of the simulations are extensively tested and
evaluated. These tests include student interviews in addition to actual utilization of the simulations
in a variety of settings, including lectures, group work, homework and lab work. The rating
system indicates what level of testing has been completed on each simulation.
All PhET simulations are freely available from the PhET website and are easy to use and incorporate
into the classroom. They are written in Java and Flash, and can be run using a standard web browser
as long as Flash and Java are installed.
Research answers to commonly asked questions:
"Can PhET sims replace real lab equipment?"
Our studies have shown that PhET sims are more effective for conceptual understanding; however,
there are many goals of hands-on labs that simulations do not address. For example, specific skills
relating to the functioning of equipment. Depending on the goals of your laboratory, it may be more
effective to use just sims or a combination of sims and real equipment
"Do students learn if I just tell them to go home and play with a sim?"
Most students do not have the necessary drive to spend time playing with a science simulation
(they're fun, but not that fun) on their own time unless there is a direct motivation such as their
grade. This is one of the reasons we are pursuing the project of how to best integrate sims into
homework.
"Where is the best place to use PhET sims in my course?"
We have found PhET sims to be very effective in lecture, in class activities, lab and homework. They
are designed with minimal text so that they can easily be integrated into every aspect of a course.
26/29
Our immediate interests are





Use of analogy to construct understanding: Students use analogies in sims to make sense of
unfamiliar phenomena. Representations play a key role in student use of analogy.
Simulations as tools for changing classroom norms: Sims are shaped by socio-cultural norms
of science, but can also be used to change the traditional norms of how students engage in
the classroom.
Specific features of sims that promote learning and engaged exploration: Our design
principles identify key characteristics of sims that make them productive tools for student
engagement. Now we wish to study in detail how each feature impacts student
understanding.
Integrating simulations into homework: Simulations have unique features that are not
available in most learning tools (interactivity, animation, dynamic feedback, allow for
productive exploration)
Effectiveness of Chemistry simulations: We have just begun investigating the envelope of
where and how chemistry simulations can be effective learning tools.Publications and
Presentations
Important features for effective simulation design (predominantly interview data)








Factors promoting engaged exploration with computer simulations , N. S. Podolefsky, K. K.
Perkins, and W. K. Adams, Phys. Rev. ST Phys. Educ., Res. 6, 020117, 2010.
Computer simulations to classrooms: tools for change , N. S. Podolefsky, K. K. Perkins and
W. K. Adams, 2009 Physics Education Research - Conference Proceedings. AIP Press, in
review , 2010.
Student Choices when Learning with Computer Simulations , N. S. Podolefsky, K. K. Perkins
and W. K. Adams, 2009 Physics Education Research - Conference Proceedings. AIP Press, in
review , 2010.
What Levels of Guidance Promote Engaged Exploration with Interactive Simulations? , W. K.
Adams, A. Paulson and C. E. Wieman, PERC Proceedings, 2009.
A Study of Educational Simulations Part I - Engagement and Learning , W. K. Adams, S.
Reid, R. LeMaster, S. B. McKagan, K. K. Perkins, M. Dubson and C. E. Wieman , Journal of
Interactive Learning Research, 19(3), 397-419 , July 2008.
A Study of Educational Simulations Part II - Interface Design , W. K. Adams, S. Reid, R.
LeMaster, S. B. McKagan, K. K. Perkins, M. Dubson and C. E. Wieman, Journal of Interactive
Learning Research, 19(4), 551-577 , October 2008.
Developing and Researching PhET simulations for Teaching Quantum Mechanics , S. B.
McKagan, K. K. Perkins, M. Dubson, C. Malley, S. Reid, R. LeMaster, and C. E.
Wieman,American Journal of Physics, 76, 406 , May 2008.
Research-Based Design Features of Web-based Simulations , W. K. Adams, N. D.
Finkelstein, S. Reid, M. Dubson, N. Podolefsky, C. E. Wieman, R. LeMaster, Talk presented
at AAPT Summer Meeting, 2004.
Research on in-class use


Teaching Physics using PhET Simulations , C. Wieman, W. Adams, P. Loeblein, and K.
Perkins, The Physics Teacher, in press, 2010.
A Research-Based Curriculum for Teaching the Photoelectric Effect , S. B. McKagan, W.
Handley, K. K. Perkins, and C. E. Wieman, American Journal of Physics, 77, 87, January 2009.
27/29






High-Tech Tools for Teaching Physics: the Physics Education Technology Project , N. D.
Finkelstein, W. K. Adams, C. K. Kller, k. K. Perkins, C. E. Wieman and the PhET Team,Journal
of Online Teaching and Learning, September 2006.
Assessing the Effectiveness of a Computer Simulation in Introductory Undergraduate
Environments , C. J. Keller, N. D. Finkelstein, K. K. Perkins, and S. J. Pollock, PERC
Proceedings, 2006.
When learning about the real world is better done virtually: a study of substituting computer
simulations for laboratory equipment , N.D. Finkelstein, W. K. Adams, C. J. Keller, P. B. Kohl,
K. K Perkins, N. S. Podolefsky, S. Reid, R. LeMaster , Phys. Rev. ST Phys. Educ. Res. 1,
010103, 2005.
Assessing the effectiveness of a computer simulation in conjunction with Tutorials in
Introductory Physics in undergraduate physics recitations , C. J. Keller, N.D. Finkelstein, K. K.
Perkins, and S. J. Pollock, PERC Proceedings, 2005.
Incorporating Simulations in the Classroom - A survey of Research Results from the Physics
Education Technology Project , K. K. Perkins, W. K. Adams, N. D. Finkelstein, M. Dubson, S.
Reid, R. LeMaster and C. E. Wieman, Talk presented at AAPT Summer Meeting, 2004.
Can Computer Simulations Replace Real Equipment in Undergraduate Laboratories? ,N. D.
Finkelstein, K. K. Perkins, W. Adams, P. Kohl, and N. Podolefsky, PERC Proceedings, 2004.
About PhET sims












An interactive optical tweezer simulation for science education , T. T. Perkins, C. V. Malley,
M. Dubson, and K. K. Perkins , Proc. of SPIE Vol. 7762, 776215, 2010.
Making Science Simulations and Websites Easily Translatable and Available Worldwide:
Challenges and Solutions , W. K. Adams, H. Alhadlaq, C. V. Malley, K. K. Perkins, J. B. Olson,
F. Alshaya, S. Alabdulkareem, and C. E. Wieman , Journal of Science Education and
Technology, accepted, 2010.
Laptops and Diesel Generators: Introducing PhET Simulations to Teachers in Uganda ,Sam
McKagan, The Physics Teacher, 48, 63-66, January 2010.
Student Engagement and Learning with PhET Interactive Simulations , W. K.
Adams,Multimedia in Physics Teaching and Learning Proceedings, 2010.
Making On-Line Science Course Materials Easily Translatable and Accessible WorldWide:
Challenges and Solutions , W. K. Adams, H. Alhadlaq, C. V. Malley, K. K. Perkins, J. B. Olson,
F Alshaya, S. Alabdulkareem, C. E. Wieman , Multimedia in Physics Teaching and Learning
Proceedings, 2009.
Making On-Line Science Course Materials Easily Translatable and Accessible Worldwide:
Technical Concerns , C. V. Malley, J. B. Olson, Multimedia in Physics Teaching and Learning
Proceedings, 2009.
PhET: Simulations That Enhance Learning , C.E. Wieman, W.K. Adams, K.K.
Perkins,Science, 322/682-683 , October 2008.
Oersted Medal Lecture 2007: Interactive simulations for teaching physics: What works, what
doesn't, and why , C.E. Wieman, K.K. Perkins, W.K. Adams, American Journal of Physics, 76,
393 , May 2008.
PhET: Interactive Simulations for Teaching and Learning Physics , Katherine Perkins, Wendy
Adams, Michael Dubson, Noah Finkelstein, Sam Reid, Carl Wieman, Ron LeMaster , The
Physics Teacher, 44(1), 18 , 2006.
A Powerful Tool For Teaching Science , C. E. Wieman and K. K. Perkins, Nature Physics,p.
290-292 , May 2006.
Transforming Physics Education , C. E. Wieman and K. K. Perkins, Physics Today,November
2005. (pdf)
Free On-line Resource Connects Real-life Phenomena to Science , K. K. Perkins and C. E.
Wieman, Physics Education, p. 93-95, January 2005.
28/29


The Physics Education Technology Project: A New Suite of Physics Simulations , K. K.
Perkins, W. K. Adams, N. Finkelstein, R. LeMaster, S. Reid, M. Dubson, N. Podolefsky, K.
Beck and C. Wieman, Poster Presented at AAPT Summer Meeting, 2004.
Should a Fortran-savvy educator learn Java, Flash, both, or neither? , M. Dubson, Talk
presented at AAPT Summer Meeting, 2004.
Students Perceptions About Learning











Students know what physicists believe, but they don't agree: A study using the CLASS
survey , Kara E. Gray, Wendy K. Adams, Carl E. Wieman, and Katherine K. Perkins,Physical
Review Special Topics, November 2008.
A deeper look at student learning of quantum mechanics: the case of tunneling , S. B.
McKagan, K. K. Perkins, and C. E. Wieman, Physical Review Special Topics: PER, 4,
020103 , October 2008.
Why we should teach the Bohr model and how to teach it effectively , S. B. McKagan, K. K.
Perkins, and C. E. Wieman, Physical Review Special Topics: PER, 4, 010103 , March 2008.
Reforming a large lecture modern physics course for engineering majors using a PER-based
design , S. B. McKagan, K. K. Perkins, and C. E. Wieman, Proceedings of the Physics
Education Research Conference 2006, 2007.
A new instrument for measuring student beliefs about physics and learning physics: the
Colorado Learning Attitudes about Science Survey , W. K. Adams, K. K. Perkins, N.
Podolefsky, M. Dubson, N. D. Finkelstein and C. E. Wieman, Phys. Rev. ST Phys. Educ. Res.
2, 010101, 2006.
Exploring Student Understanding of Energy through the Quantum Mechanics Conceptual
Survey , S. B. McKagan and C. E. Wieman, PERC Proceedings 2005, 2006.
Towards characterizing the relationship between students' interest in and their beliefs about
physics , K.K. Perkins, M.M. Gratny, W.K. Adams, N.D. Finkelstein and C.E. Wieman, PERC
Proceedings, 2005.
The surprising impact of seat location on student performance , K. K. Perkins and C. E.
Wieman, The Physics Teacher, 43, p. 30-33 , 2005.
Minimize Your Mistakes by Learning from Those of Others , C. E. Wieman, The Physics
Teacher, 43, 252-253 , 2005.
The Design and Validation of the Colorado Learning Attitudes about Science Survey , W. K.
Adams, K. K. Perkins, M. Dubson, N. D. Finkelstein and C. E. Wieman, PERC
Proceedings, 2004.
Correlating Student Beliefs With Student Learning Using The Colorado Learning Attitudes
about Science Survey , K. K. Perkins, W. K. Adams, N. D. Finkelstein, S. J. Pollock, and C. E.
Wieman, PERC Proceedings, 2004.
Assignment
Explore http://phet.colorado.edu/en/simulation/moving-man , the Phet simulation of a moving man.
In the basic level of the simulation position, velocity and acceleration are being visualized
throughout the linear motion of a man. The didactical advantage of the simulation is that the
meaning of positive and negative values of position, velocity and acceleration is linked to the real life
movement. In a second level the graphical information is added. Pupils most of the time find it very
difficult to link the abstract vector quantities position, velocity an acceleration to reality. The
simulation provides a tool to construct the link.
Report of your reflection on the use in a word document. Upload the document to Toledo.
29/29