Ontological Analysis of the Concepts of Energy and Energy Conservation and Its Educational Implications

Transkript

1 New Physics: Sae Mulli (The Korean Physical Society), Volume 61, Number 9, , pp DOI: /NPSM , ( , , ),.. כ,,... כ כ.. :,,,, Ontological Analysis of the Concepts of Energy and Energy Conservation and Its Educational Implications Yong Wook Cheong Jinwoong Song Department of Physics Education, Seoul National University, Seoul (Received 8 June 2011 : revised 12 August 2011 : accepted 23 August 2011) Although energy and energy conservation are fundamental concepts in physics, students have serious difficulty in learning these complex concepts. This study systematically analyzed the concept of energy and its conservation to get a comprehensive view of the concepts. For that purpose, we analyzed fundamental dynamical relationships in physics with a focus on the relationship among ontological categories such as system, property, and interaction. Based on the analysis, we discuss the epistemological aspect of energy concepts. Then, we extract six core ideas inherent in energy concepts and elaborate the meaning of each idea. Further, we discuss in detail two aspect of energy conservation: energy transfer and energy transformation. Through the analysis and discussion, we show that consideration of the ontological categories and of the relationships among them is essential for a comprehensive understanding of energy. Finally, based on the results of our study, we discuss the possible educational implications for teaching energy concepts. PACS numbers: F Keywords: Energy, Energy conservation, Ontological category, Ontological causal relation, Dynamical relationship zimusa@snu.ac.kr -850-

2 -851- I. כ [1, 2].,. כ, [2 4]., [5 8]. [7,8]. כ [2,5, 9 13]. [9 13]. 1.. כ. [2,4,15]. כ [2,15]. [16,17]., כ [5,15].., [13]., [9 13,19 21]. Hestenes Halloun כ ( ) [19,20]. [2,9 13]., כ.,. [2 13].. כ...,,,,. כ,. כ., [9,16]. כ. [9 13,19 21]., כ,. כ....

3 -852-, Volume 61, Number 9, II. : [15]. Chi כ [16,17]..,. [9 13,19 21]. [8,16]. כ...,,. 1. [9, 16, 19 21]. Arons [9]. Arons,. Arons (system), (property), (interaction) [9]. (object),. כ,,.,, ( ). כ, [9]. כ.... כ כ. ( ) [9]. ( ) כ. כ... Arons,,, [9]. 2. כ. 1 כ.. כ..,.,..

4 -853- Table 1. Various dynamical relationships in physics. Dynamical Relationship Cause (action) Effect (state change) Mathematical Relationship Newton s 2nd law net force acceleration F = ma Impulsion momentum theorem impulse change of momentum I = p ( F dt = mv ) ( ) Work Energy theorem work change of kinetic energy W = K F d = 1 2 mv2 First thermodynamic law work & heat change of internal energy of a system W + Q = E int,.. A B B A. כ. -.. כ..., (environment)..,.,. כ.,. כ. כ כ, כ. F, I, W, Q, (a), ( p), ( K), ( E int ) ( ). 1 1 W +Q = E int Q = E int + W. W. Q = E int + W, כ., Q = E int + W W + Q = E int 1 כ., ( = )... כ. 1..

5 -854-, Volume 61, Number 9, כ.,,, כ. 1 (W +Q = E int ). כ., 1 ( ), (,,.). - ( ) = ( ) (W = K) כ. כ.,,, [16,17] כ... Arons (=), [9]. Etkina [21]. (state equation). x = x 0 + v o t. (causal equation) כ. Etkina, Halloun [20]., (F = GmM/r 2 ).. כ כ. כ. כ. כ. כ [22]. כ.,,, כ [22]. כ.. כ. 1, כ

6 כ. 1 - כ, -. כ. 2. כ. III.. כ.. 1. [2,8,23]. Warren,, כ [8]. Driver (a way of look at), [2].. Papadouris (transphenomenological), [23]. כ [2,23],.... כ, כ, כ.,,,. ( ).,,.. כ כ, ,.. 2.

7 -856-, Volume 61, Number 9, Table 2. Six core ideas on the conceptual structure of energy. Idea 1 Idea 2 Idea 3 Idea 4 Idea 5 Idea 6 Energy is a kind of abstract property of a system and it is an extensive quantity. Energy can have various forms; various forms of energy are related to various phenomenological properties. Various kinds of interaction on a system cause the energy-change of the system. Energy of a closed system is conserved. Energy can be transferred from one system to the other system. Energy of a system can be transformed from one form of energy to the other form of energy. Table 3. Correspondence between the forms of energy and phenomenological properties. Form of Energy Formal Expression Corresponding Phenomenological Property 1 Kinetic energy 2 mv2 Velocity or Speed Internal energy E int Temperature Potential energy GmM, 1 r 2 kx2, Spatial arrangement (relative position) among the entities in a system. 1. W + Q + T MT + T ER + = K + U + E int (1) Jewett כ [13].. W, Q, T MT, T ER (1). כ. K, U, E int. (1). (1). [2 13],, 2. כ. כ. 1 כ [11]. כ., (extensive quantity). 2, כ.... (1),, 3. ( ),, ( ).. כ...

8 -857- כ..,,. 2 כ כ. (W ), (Q), (T MT ), ( ) (T ER ).. כ , 5, 6.,. כ 4 כ. כ [11].,.. כ. כ , כ כ.,, כ... כ, כ.... (Joule) ( ) ( )..., כ. כ 3, 6.

9 -858-, Volume 61, Number 9, כ. IV. : 4, 5, כ [2,11],. ( 1 2). 1 2 E 1, E 2,. T 1, T 2 (T 1 < T 2 ), Q 1, Q E 1 + E 2 = 0 1. Q 1 = E 1, Q 2 = E 2 כ כ ( Q 1 +Q 2 = 0). T 1 < T 2, 1 2.,,,, (,, )., [3,24]..,.,,,. (,, ). (,, ). כ כ.. כ.. E 1, E 2 U 12.,. E 1 + E 2 + U 12 = 0.. E 1 + E ( ). כ. 1 (W + Q = E). 1 E.. 1 (1).

10 -859-,. 1 2 K 1, K 2, W 1, W 2.. W 1 = K 1, W 2 = K 2,.. W 1 + W 2 = K 1 + K 2 0. U 12.. (K 1 + K 2 ) (U 12 )...,. כ.. V כ... [11]... כ. כ. 1 כ כ, 1. כ כ. 1 כ. [9 13, 19 21].

11 -860-, Volume 61, Number 9, , [18]., כ.. כ כ... [5].., כ. כ.. כ,, כ. [12].. כ. 1 (W + Q = E int ) W W כ. Q. Q כ.. Q Q. Q כ. כ כ כ. VI. כ.., כ.... כ כ.. כ.,,. [5 8] כ..,. כ..

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