Development of a hands-on model embedded with guided inquiry laboratory to enhance students’ understanding of law of mechanical energy conservation

A single group pretest-posttest design was employed in this study (Figure 1). This design allows the purpose of comparing and measuring the change in the group(s) due to the experimental treatment (Dimitrov & Rumrill, 2003). Using a purposive sampling, a total of 30 grade ten students from one of the middle secondary schools in western Bhutan were involved in this study.

A learning laboratory based on a guided inquiry approach that falls under the framework of constructivism theory was used as a treatment. Under this approach, a simple hands-on model that formed an integral part in demonstrating the law of mechanical energy conservation was introduced. The guided inquiry laboratory that was designed for 120 minutes comprised of four main phases: (i) posing scientific questions; (ii) formulating hypothesis; (iii) gathering data through experiment and, (iv) presenting findings and conclusion. Before the intervention, the pretest that comprised of 13 two-tier multiple items were administered for 20 minutes. The participants were then allowed to explore and demonstrate the law of mechanical energy conservation under the framework of a guided inquiry method for 80 minutes. Students were divided into a group of 5 members each. The role of a teacher was to facilitate and direct the students towards achieving the objective of their experiment. Strictly based on the four phases, the teacher first posed a couple of scientific questions and encouraged the students in formulating the hypothesis. The set of question was related to what they were supposed to find out and explain after doing the experiment using the hands-on model. The students were then directed to investigate their hypothesis in groups by using the hands-on model following the guided laboratory instructions provided in each group. Through the experiment, each group gathered and analyzed the data they obtained using the hands-on model and compared with the set of hypothesis they made during the first phase. Each group then compiled their findings and presented to the entire class for discussion and confirmation. The students were made to attend the posttest that comprised of parallel two-tiers multiple-choice items used during the pretest for 20 minutes.

Furthermore, Figure 2 shows the framework of this study, and following are the scientific questions posed to the students in students’ worksheets. The questions are used to facilitate the students for setting of hypothesis and gathering data to test their hypothesis.

Activity I: Setting Hypothesis
(To save time, the teacher will guide the students to set the hypothesis)

Based on the diagram below,

1. What form of energy is there when the ball is at point A?

2. What kind of energy change takes place when it moves from point A to point B?

3. How can you explain that the energy of this object is conserved?

4. Can you define the law of conservation of mechanical energy?

Data Collection:

Trolley mass, m =………....kg

Acceleration due to gravity, g = 9.8 ms^-2

Length of the picket fence, d= 0.04 m

The table to calculate total mechanical energy

Potential Energy
Kinetic Energy

Total Mechanical Energy

Points

Mass
(kg)

E_p=mgh
(J)

t
(s)

v (m/s²)

E_k=½mv² (J)

E_total= E_p + E_k
(J)

1

2

3

4

5

(Graph paper will be attached here)

Now let us answer the following questions:

Questions	Answers
1. Can we create the energy?
2. Can we destroy energy?
3. Do you think that the total mechanical energy is conserved?
4. Can you give some examples of conservation of mechanical energy
5. How can you define the law of conservation of mechanical energy after your experiment?
6. Is the energy conserved according to your experiment? How did you know that the energy is conserved?

A simple hands-on model designed in a form of an inclined plane was used to demonstrate the law of mechanical energy conservation. Inclined plane is one of the most commonly used examples in the textbooks of the Bhutanese science curriculum to explain the law of mechanical energy conservation. Hence, doing an experiment to demonstrate the law of mechanical energy conservation with a realistic hands-on model would be easier and fun learning for the students. A long acrylic ramp of 0.78 m was used to make an inclined plane for the object to move. Acrylic was preferred for its durable and frictionless nature when compared to other locally available materials. Five photogate sensors which were used to detect the time (Δt: Δt→0) for calculating the instantaneous velocity of a moving trolley (v_int) were embedded in the ramp. Photogates were used because the determination of physical quantities like velocity and acceleration are almost precisely done by it (Galeriu, 2013). Each end of the photogate sensors were connected to the timer that displayed the time (Δt) taken by the object to pass through the arms of each photogate sensors in milliseconds. The sensors were located at a distance of 0.05 m from each other and represented five different heights (h_int) represented as h₁, h₂, h₃, h₄ and h₅ as shown in the Figure 3. An object here was a frictionless wheeled trolley with a fixed mass (m). The mass of an object (in this case the trolley) was fixed so that the students can concentrate more on demonstrating the law of mechanical energy conservation rather than calculating mass of an object. Underneath the trolley, a picket fence of 0.04 m (Δd) was attached for the purpose of time detection (Δt) when the trolley passing through each sensor point to calculate the instantaneous velocity (v_int= Δd/Δt). The mass and the acceleration due to gravity g were constant with 0.301 kg and 9.8 ms^-2 respectively. As the students allow the trolley to move from the top of the ramp, the picket fence attached beneath the trolley passes through the arms of the photogate sensors. The sensors instantly record the time at which the trolley passes and this time in milliseconds is shown in a monitor. Using these variables, they were guided to calculate the potential and kinetic energy using the relations E_p=mgh_int and E_k=½mv². The sum of these energies at each point represented the total mechanical energy for the corresponding heights (E_total= E_p + E_k).

Figure 3. A hands-on model developed to demonstrate the law of mechanical energy conservation.

The data were collected using the research instruments namely Conceptual Evaluation Test for Law of Mechanical Energy Conservation (CETMEC) and the Learners Attitude Questionnaire for Law of Mechanical Energy Conservation (LAQMEC). The CETMEC which consisted of 13 parallel two-tier multiple-choice items was used to investigate the students’ conceptual understanding of the law of mechanical energy conservation. There were 13 parallel items in a form of the two-tier multiple-choice format used for both pretest and posttest. Except for three items (item 1, 7 and 12), the remaining 10 items were adapted from American Association for Advancement of Science (AAAS Project 2061). The items 1, 7 and 12 were self-created. The ten items adapted from AAAS Project 2061 were in the form of multiple-choice questions that were used to study the understanding of energy and energy conservation for grade 7-12 (Herrmann-Abell & DeBoer, 2011; Trumper et al., 2000). However, in this study, those items have been modified into two-tier multiple choice based on the format discussed by Treagust (1986). In doing so, the adapted items were either used to find the conceptual understanding in the first tier or to determine the reasoning and thinking skills in the second tier. But in both the tiers, it was a multiple choice that had only one correct answer. The first tier had three choices including “I don’t know” since the subjects during the pretests were assumed to be unfamiliar with concepts because they were not exposed to treatment (Yu, 2001). In the second tier, it consisted of five possible reasons to support the choice the students made in the first tier but only one of these reasons was correct. The rest of the reasons were either the misconceptions gathered from the literature (AAAS, 2016) or through the personal classroom teaching experiences. The CETMEC items were used before the treatment of a developed guided inquiry laboratory as the pretest and as the posttest after the treatment by reshuffling the items. The Table 1 shows how each item was constructed to measure the different constructs in this study.

The LAQMEC consisted of 20 closed-ended items based on the five-point Likert scale and included an open-ended item. All the items were constructed considering the characteristics of a guided inquiry approach which falls under the constructivist view of learning. This instrument was used after the treatment to investigate the views and attitudes of the students towards the learning laboratory and also to find the effectiveness of the developed hands-on model. For the Likert scale rating, the lower the number students score, greater was the degree of non-agreement with the statement. So, the score 1 meant “Strongly Disagree”, 2 as “Disagree”, 3 to be “Neutral”, 4 denoted “Agree”, and 5 meant “Strongly Agree”. The scores for the negative statements were interpreted using a reverse coding. There were six constructs (see Table 2) out of which the five constructs namely Topic of the Lesson, Teacher, Classroom Activities, Learning Method and General Classroom Impression exclusively determined the views and opinions of the students towards the guided inquiry laboratory while the theme labeled Hands-on model assessed the students’ attitudes towards the model used to determine the law of mechanical energy conservation. The open-ended item was created to encourage the students to write any matters that they found it missing related to the law of mechanical energy conservation based on the three domains like contents (cognitive), attitude (affective) and skills (psychomotor) and etc.

Directions: Read the statements carefully. There are TWO parts in each item. In the first part, you can Tick [√] whether the statements are TRUE, FALSE or DON’T KNOW based on your opinion. In the second part, you can Tick [√] for the reason that best supports your opinion in the first part.

Imagine that an object moves from point A to B which are at a same height in a horizontal direction. Suppose that there is no transfer of energy from ball to the track or from ball to the air, the total mechanical energy of a ball at point B will remain same as the point A.

a) True b) False c) I don’t know the answer

The reason for my answer is

Whether more or less, it will depend on the speed of object.

The energy is more because it went down the steep side of the track.

The energy will be less because it is used as it travels.

The total energy remains unchanged in a system.

I don’t know the reason.

A teacher releases a book from a height of 1m and asks the students to compare the potential energy at points 1m, 0.5 m and on the ground. One student answered that the potential energy will be highest at 1m, less in 0.5m and zero when it is on the ground.

a) True b) False c) I don’t know the answer

The reason for my answer is

The potential energy depends on height of the object. The height is zero when the book is on the ground, hence potential energy is zero.

The potential energy does not depend on height. So, it is equal in all the points.

The potential energy is maximum when the book is on the ground since it travels with a huge velocity.

The potential energy is lost as the book slowly falls on the ground.

I don’t know the reason.

The instruments were thoroughly validated by five experts from Bhutan and Thailand who had experiences of teaching Physics for a minimum of 3 years in higher and university levels respectively. The Item-Objective Congruence index (IOC) were determined and the majority of the items from the CETMEC and LAQMEC were determined to have IOC Index more than 0.8 which signified a strong correlation (Rovinelli & Hambleton, 1976). Hence, those items were accepted while few items having IOC index lower than 0.8 were revised according to the expert’s comments. After validation was over, it was piloted with 30 higher secondary science students who have already learnt about the law of mechanical energy conservation. The reliability coefficient (Cronbach’s alpha) of the pilot study was 0.77 indicating that the items were favorable for the implementation (Tavakol & Dennick, 2011; Bland & Altman, 1997).

The means of both pretest and posttest were compared using a paired sample t-test. To further support the findings, the level of students understanding (Abraham, 1994) were determined. The CETMEC items were analyzed using the assessment criteria modified from Chou, Chan, & Wu (2007) as shown in Table 3.

Since this study included “I don’t know” as an option in both the tiers, students who opted this option in both the tiers were given 0 points. On the other hand, 1 point was awarded only when the choice in the first tier was correct with wrong/no or I don’t know in the second tier. If the reason in the second tier was correct with incorrect/no or I don’t know as the choice in the first tier, then it was marked 0 points. This was because in reality it had very limited chance to happen owing to the nature of second tier items that were based on reasoning and demanded higher thinking and analytical ability. Even if the reason was correct, it was assumed as students guessing the reasons without first knowing the simple choice in the first tier.

The students’ responses were then further classified into levels of understanding which was modified from Abraham, Williamson, and Westbrook (1994) as shown in Table 4.

The four levels of understanding namely Sound Understanding (SU), Partial Understanding with Specific Alternate Conception (PUSAC), Specific Alternate Conception (SAC) and No Understanding (NU) were used in this study. Thus, the students’ answers that included all components of the validated response with correct choice in the first tier and correct reason in the second tier classified as Sound Understanding (SU). The responses with a correct choice in the first tier but with an incorrect or no/I don’t know reason in the second tier were grouped as Partial Understanding with Specific Alternate Conception (PUSAC) because these responses showed understanding of the concept but also showed some misunderstandings due to incorrect reasons in the second tier. Similarly, the responses that had incorrect/no choice or I don’t know in the first tier but with a correct reason in the second tier were considered as Specific Alternate Conception (SAC) because such responses indicated an illogical and incorrect information. Logically, it was deemed impossible for the students to get correct reasons in the second tier that demanded higher analytical ability without having clearly understood the first tier that contained only knowledge statements. Such kind of learning is not meaningful but rather it is due to a rote learning or superficial learning (Bayrak, 2013). Thus, even if the responses were correct, it was attributed to be simply a guess. Likewise, if the responses contained wrong or I don’t know in both the tiers, incorrect choice with I don’t know in the second tier or I don’t know in the first tier with incorrect reason in the second tier, it was classified as having No Understanding (NU).

Similarly, for the LAQMEC, the means and the standard deviations of each construct were determined to examine students’ attitudes toward the guided inquiry laboratory. The mean of the items with negative statements was reversely coded.

Items	Constructs
1, 2, 3, 4, 9	Energy conservation
5, 6, 7, 8	Energy is created or destroyed
10, 11, 12, 13	Energy is transferred or transformed

Items	Constructs
1, 2, 3	Topic of the lesson
4, 5, 6	Teacher
7, 8, 9	Classroom activities
10, 11, 12, 13	Learning method
14, 15, 16, 17	Hands-on model
18, 19, 20	General classroom impression

Points for the response	Assessment criteria
0 points	Wrong / No / I don’t know in both the tier
0 points	Only the reason in the second tier is correct
1 point	Only the choice in the first tier is correct
2 points	Both the choice and the reason are correct

Level of understanding	Interpretation	Tier 1	Tier 2
Sound Understanding (SU)	Responses that included all components of the validated response	Correct	Correct
Partial Understanding with specific alternate conception (PUSAC)	Responses that showed an understanding of the concept, but also made a statement, which demonstrated misunderstanding	Correct	No/ Incorrect/ I don’t know
Specific alternate conception (SAC)	Responses that included illogical or incorrect information	No/ Incorrect/ I don’t know	Correct
No understanding (NU)	Repeated the question, contained irrelevant information or an unclear response; left the response blank	No/ Incorrect/ I don’t know	Incorrect/ I don’t know

Potential Energy			Kinetic Energy			Total Mechanical Energy
Points	Mass *(kg)*	E_p=mgh *(J)*	t *(s)*	v *(m/s²)*	E_k=½mv² *(J)*	E_total= E_p + E_k *(J)*
1
2
3
4
5