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Asia-Pacific Forum
on Science Learning and Teaching, Volume 10, Issue 1, Article 6
(June, 2009) |
First, summary tables and relevant explanations were given, then characteristics of the answers were examined, principally with respect to the four levels of understanding and then the subcategories related to these levels were created based upon the characteristics of the students’ answers. In addition, findings were classified under these titles:
§ Energy, power and force as concepts
§ Energy, power and force as physical quantities
§ Measurement of units of energy, power and force
§ The relation between movement and energy, power and force
§ Energy, power and force as a property of an object
Energy power and force as concepts
The level distribution of the answers given for the first question is presented in Table 1.
Table 1 The level distribution of the student answers related to definition of the energy, power and work concepts.
Concepts
Frequency
Percentile
Levels
Number of sub-categories belonging to the levels
[3]
[2]
[1]
[0]
[3]
[2]
[1]
[0]
Energy
f
%
6
11
6
11
13
23
31
55
1
2
6
-
Power
f
%
8
14
9
16
17
31
22
39
1
3
6
-
Force
f
%
9
16
5
9
8
14
34
61
1
2
7
-
To answer this questions, students were expected to define energy as “an invented entity in the context of a theoretical framework for explaining changes encountered in physical systems” (Papadouris & Constantinou, 2006), power as “the amount of energy consumed/used in unit time or the rate of energy transmission in unit time” and force as “the interaction between two physical bodies causing push or pull” (Serway, 2002; Crowell, 2006).
When the student answers about energy concepts were grouped based on their characteristics (see Table 1), the majority of them (approximately 80%) fell within the first two levels (0, 1). That is, they were unable to submit any definitions for the related concepts or gave answers other than scientific ones. Half of the remaining students responded to questions scientifically (level 3), and the remaining students gave answers not completely true, but partially applicable in a scientific point of view (level 2) (11% and 11% respectively).
Similarly, the majority of student answers (70%) about power fell into the first two levels (0, 1), and only 30% of them complied with scientific definitions as presented in Table 1. Answers for force demonstrated a similar distribution. Only one-forth of the students gave answers that can be classified in level 2 and 3, and the rest either gave no answers or disclosed incorrect definitions for the concept.
The sub-categories of the levels are given in the table below.
Table 2 The sub-categories of the student answers related to definition of the energy, power and work concepts.
Level 3
Energy
Capacity for doing work
Power
Amount of work done per unit time
Force
A dynamic vector quantity that changes a body from a state of rest to one of motion, stops or redirects a moving body
Level 2
Energy
The quantity possessed by a body because of its position or movement
It is spent while an object is being carried
Power
Energy that is spent to do something
It is the velocity of energy
It is work per time
Force
Influence that is applied to give an object velocity
Vector quantity necessary for doing work
Level 1
Energy
It is the power consumed while work is being done
The conversion of force into movement or velocity
The rate of power over time
It is velocity multiplied by mass
It is the raw material used to get power
Power
The ability to do work
The force possessed,
Stored energy
The velocity of a mass
Force
Velocity applied on an object
Change in the position of an object with respect to velocity and time
The ability for using muscle power
It is power
The associate of energy and power
Ability for doing work
Considering this table, the content of the answers classified in the level 2 showed that the students had appropriate perceptions about the energy, power and force; however, they had difficulties in expressing their knowledge. And the expressions considered in level 1, on one hand, shows that the energy, power and force concepts were not perceived scientifically by students and also there were confusions over the meaning of these concepts.
Energy, power and force as physical quantities
The classifications given as responses to the second question, which was asked to determine knowledge of quantities of energy, power and force concepts, were presented in Table 3.
Table 3 The distribution of the student answers related to the kind of quantity (Vector/Scalar) of energy, power and force.
Concepts
Frequency
Percentile
Levels
Sub-categories of the levels
[3]
[2]
[1]
[0]
[3]
[2]
[1]
[0]
Energy
f
%
11
19
2
4
3
5
40
72
1
1
2
3
Power
f
%
18
32
-
-
8
14
30
54
2
-
3
3
Force
f
%
19
34
1
2
4
7
32
57
1
1
1
2
The students were expected to answer this inquiry by stating concepts, for example, normally force is vector, but energy and power are scalar quantities. In addition to such an answer, students were also expected to write an explanation. For example, energy and power are not quantities with direction and magnitude, however, force is a quantity with direction and magnitude.
As seen from Table 3, a considerable majority of the students were at the level 0(72% for energy, 54% for power and 57% force), since they did not give any answers for the question or only responded, “it is a scalar/a vector quantity.” On the other hand students gave answers coinciding with scientific facts and qualified as level 3; 19% for energy, 32% for power and 34% for force, respectively. Regarding energy (4%) and force (2%), a minority of students gave answers that did not fully match, but were compatible with scientific facts. Finally, Table 3 also shows that for energy (5%), power (14%) and force (7%) slightly more students gave answers that did not match the scientific facts at all and were classified as level 1.
The sub-categories related to the kind of quantity of the concepts considered are listed below.
Table 4 The sub-categories of the student answers related to the kind of quantity (Vector/Scalar) of energy, power and force
Level 3
Energy
Direction is not important
Power
Direction of power is not important
Power is scalar
Force
Force has direction and magnitude
Level 2
Energy
It is scalar because it has a magnitude
Force
It is vector because it depends on velocity
Level 1
Energy
Since force is vector, energy is also vector
It is a magnitude with direction, it is important towards which way it is applied
Power
It is the product of two vectors (Fx)
It affects in a certain direction
Since force has direction
Force
It has three dimensions
Level 0
Energy
Energy is scalar
Energy is a vector quantity
No answers
Power
Power is a scalar quantity
Power is a vector quantity
No answers
Force
Force is a vector quantity
No answers
Some of the students fell into the level 2 and reported that energy is scalar and force is a vector quantity and most of them could not explain their answers in a scientifically acceptable way. The students classified in level 1 and figuring energy and power as vector quantities can be said to have significant misconceptions. In spite of the fact that the rest of the students in this group reported that force is a vector quantity, their explanations were not valid from a scientific point of view.
Considering level 0, Table 4 shows that three types of answers are considered in this level: correct answers with no explanation, wrong answers with no explanation and no answer. For the concept of energy, most of the students placed into this category (65%) said that energy is scalar without providing any explanations; 2% claimed that energy is a vector quantity without any explanation; and the rest (33%) submitted no answers. For the concept of power, 63% of the students evaluated in this level noted that power is a scalar quantity and put forward no explanations; 1% said it is vector quantity; and the rest (26%) left the question unanswered. As for the concept of force, 56% of the students in level 0 argued that force is a vector quantity, and the remaining 44% did not respond the question in any way.
When we try to evaluate all the categories collectively, it can be said that the students did not have adequate and correct information about whether the energy, power and force concepts are vector or scalar quantities. However, the students were relatively successful at determining that the force concept is a vector quantity.
The Measurement of Units of Energy, Power and Force
Table 5 presents the classification of the student answers given for question three inquiring about the students’ state of determining the measurement of units of energy, power and force. Based upon this data, more than half of the students were classified in level 3 as a result of their answers matching the scientific facts (56% for energy, 54% for power, 57% force). For this question, related to energy, only 5% of the students gave answers that did not match the scientific facts and placed at level 1. However, there were no students at this level for the other concepts. Additionally, Table 5 presents that students could not write the measurement units and they were classified as level 0 (for energy 39%, for power 46% and for force 43%).
Table 5 The distribution level of the student answers about the units of energy, power and force
Concepts
Frequency
Percentile
Levels
Number of sub-categories belonging to the levels
[3]
[2]
[1]
[0]
[3]
[2]
[1]
[0]
Energy
f
%
31
56
-
3
5
22
39
4
-
-
-
Power
f
%
30
54
-
-
26
46
2
-
-
-
Force
f
%
32
57
-
-
24
43
3
-
-
-
The answers, about the units of energy, power and force, related to the mentioned four levels are presented in Table 6.
Table 6 The sub-categories of the student answers related to the units of energy, power and force
Level 3
Energy
Joule
Erg
Calorie
Nt.m
Power
Watt
J/s
Force
Newton
Dyne
kg.m/s2
Level 1
Energy
km/s
It has no unit
The relation between movement and energy, power and force
Under this title, student views about the relation between movement and energy, power and force were examined.
Table 7 The distribution level of student answers about the relation between movement and energy, power and force
Concepts
Frequency
Percentile
Levels
Number of sub-categories belonging to the levels
[3]
[2]
[1]
[0]
[3]
[2]
[1]
[0]
Energy
f
%
7
12
3
6
7
12
39
70
1
2
2
3
Power
f
%
-
3
6
19
34
34
60
-
1
8
3
Force
f
%
6
11
2
4
7
12
41
73
1
1
4
3
As seen from Table 7, the vast majority of student answers fell into level 1 and 0 for this question (i.e. answers did not match the scientific facts or no answer). Similarly, for the energy and force concepts (12% of students) and for power concepts(34% of the students), students gave answers that did not match scientific facts (level 1). It was determined that the rest of the students failed to answer (70% for energy, 60% for power, 73% force). They did not submit any answers aiming to explain the relationship between the related concepts and movement (level 0). However, only 12% of the students for energy and 11% for force could give answers matching the scientific facts and were classified as level 3. None of the students could give scientific answers about the concept of power. 6% of the students for energy and 4% of the students for force gave answers not matching, but agreeable with scientific facts and qualified as level 2.
The table below summarizes the sub-categories related to this issue.
Table 8 The sub-categories of the student answers about the relation between movement and energy, power and force
Level 3
Energy
The movement is done by energy
Force
Force generates movement
Level 2
Energy
Energy can neither be created nor be destroyed
Potential energy can come out without movement
Power
Movement requires power to be created
Force
Movement comes out by energy but not force
Level 1
Energy
No energy comes out without movement or action
Energy is ability for doing work. No energy is generated if there is no movement
Power
We lose certain amount of energy to do a work or action
It is a result of energy in an engagement
Power is spent or generated if something happens
Power is the force which is necessary to perform a movement,” Power can not be spent without energy consumption
It is not possible without interaction, power is needed to generate movement
Movement is a kind of power
Since there is no self-generated force, no power can come out without movement
Level 0
Energy
Energy is a result of movement
Energy is not a result of movement
No answers
Power
Movement is the source of power
Power is the source of movement
No answers
Force
Movement is the source of force
Force is the source of movement
No answers
The answers categorized in level 3 shows that there were no answers for power in this level. The students were observed as having difficulties especially on whether the power concept has a role in generating movement. The answers qualified as level 2 were true but not adequate answers to the question asked. And the answers categorized in level 1 showed that students had some misperceptions about the generation of movement.
There were different types of answers classified in level 0 . For energy, more than half of the students that fell into this category (54%) reported that energy is a result of movement with no explanation. Again, 10% argued that energy is not a result of movement with no explanation, and the rest (36%) did not answer this question. Concerning the power concept, the majority of the students evaluated in this level either said that movement is the source of power without explaining (68%), or stated that power is the source of movement with no explanation (6%). The rest of the students (26%) did not answer the question. For the concept of force, 34% of the students placed into this category stated that movement is the source of force with no supporting explanation, 15% of them again reported, with no explanation, that force is the source of movement and the rest of the students (51%) left the question unanswered.
Energy, power and force as a property of an object
Classification and distribution of student answers regarding the relationships between the concepts of energy, power and force as properties of an object are presented in Table 9.
Table 9 Classification and Distribution of the Student Answers about the Relationship between the Energy – Power – Force Concepts as Property of an Object
Concepts
Frequency
Percentile
Levels
Number of sub-categories belonging to the levels
[3]
[2]
[1]
[0]
[3]
[2]
[1]
[0]
Energy
f
%
-
1
2
3
5
52
93
1
-
3
3
Power
f
%
-
2
4
4
7
50
89
-
2
4
3
Force
f
%
-
-
5
9
51
91
-
-
5
3
As seen in Table 9, none of the participants gave answers matching the scientific facts related to the question about the state of the energy, power and force concepts as a property of an object. Moreover, only 2% of the students for energy and 4% for power gave answers partly coinciding with scientific facts. These students were classified in level 2. Furthermore, for energy (5%), for power (7%) and for force (9%), a minority of the students submitted non-scientific information to explain the relationship between the concepts and objects; they were labeled as level 1. And finally, the vast majority of students fell into level 0 by either giving short answers with no explanation or not answering the question (respectively; 93%, 89% and 91%).
The table below summarizes the students’ answers about the relationship between the energy - power - force concepts as property of an object.
Table 10 The sub-categories of the student answers about the relationship between the energy - power - force concepts as property of an object
Level 2
Energy
Objects are those provide energy
Power
Everything that has energy has power as well
Power belongs to the object
Level 1
Energy
Energy is changeable
Everything has energy in different quantities
Energy comes from the position of molecules or objects
Power
Everything in nature is object based
Every object has different capacity
Power is ability to do something
Power does not depend on the object it depends on the magnitude
Force
Action-reaction requires this
Force is the indicator of power
It depends on the position of objects
We apply force to the matter from the outside
Everything that has mass has force
Level 0
Energy
Energy can be a property of an object
Energy cannot be a property of an object
No answers
Power
Power can be a property of an object
Power cannot be a property of an object
No answers
Force
Force can be a property of an object
Force cannot be a property of an object
No answers
Considering level 2 and level 1, Table 10 shows that students’ answers don’t coincide with the correct knowledge regarding the relationship between the energy-power-force concepts as property of an object. The rest of the answers are classified in level 0. Associated with the energy; 31% of the students in this category noted that energy can be a property of an object and gave no supporting explanation. 11% said energy cannot be a property of an object, again with no explanation, and the rest (58%) gave no answer. For power, 24% of the students remarked that power can be a property of an object, 22% argued that it cannot be a property of an object with no explanation and the rest (54%) left this question unanswered. Finally, for force, 22% of the students put forward that force can be a property of an object, 20% said it cannot be; both were without explanations. The rest (58%) gave no answers.
