LEGO-Based Physics Lab: The Potential of LEGO Bricks for Modeling in Physics

To express the potential of LEGO bricks for modeling physics phenomena in kinematics, the well-known experiment of self-graphing trajectories will be discussed.¹⁴ Using a LEGO composite assembly, I mapped the two-dimensional trajectory described by a ball after it was released from a ramp at different speeds. To minimize friction, here I used a metal ball (r = 0.0095 m), which has typically been used in laboratory courses. Three trajectories corresponding to three different departure speeds were mapped and are depicted in red, green, and white in Fig. 1(a). To trace these trajectories, three 32 × 32 baseplates were attached to a whiteboard with the help of a thin magnetic strip that was attached to the baseplates. For the construction of the curved ramp on which a ball slides, a system of two straight lines was used, each composed of 16 Pin Joiner Rounds, each coupled by means of Pins without Friction Ridges, as shown in Fig. 1(b) (top). These straight lines are flexible enough that they can be bent to form a rail on which the ball can slide.¹⁵ Both ends of each rail were connected to a Brick Modified 2 × 4 with Pins, and the other two ends were connected using a Pin Connector Perpendicular Double 3L. The result is shown in detail in Fig. 1(b) (bottom).

Once the ramp was mounted on the baseplates, three initial heights were selected from which the ball could be released; these points are shown in Fig. 1(a) in red, green, and white on the top of the ramp. These points define three different ball departure velocities with respect to the track, which lead to different parabolic trajectories. These trajectories are represented discretely by points using 1 × 1 Round Tiles, as shown in the central part of Fig. 1(a). Note that here I take advantage of the discrete gridding of the LEGO architecture to map the trajectory of the ball, which facilitates the modeling of the ball’s motion in two dimensions. Each point on the trajectory represents an average of approximately 40 repetitions corresponding to the marks left by the ball upon impact with a flat surface made of LEGO bricks with tracing paper attached to it. The flat surface with the tracing paper was repeatedly moved at a horizontal distance equal to 3 LEGO studs (2.4 cm) from its last location. The result of all the impacts that were recorded to map the ball trajectories is shown on the right side of Fig. 1(a). In the three cases studied, a quadratic trend can be observed as the ball travels the vertical distance. The dispersion of the points recorded for each case is well observed, like the pattern shown in other studies for teaching measurement and uncertainty in introductory physics laboratory courses.¹⁶ 

The traditional case addressed in introductory physics laboratories corresponds to the Atwood machine and its variants (e.g., the traditional Atwood machine¹⁷ or the modified Atwood machine¹⁸). In this section, I will use one type of the modified Atwood’s machine as an example to express the potential of LEGO bricks for modeling mechanics phenomena in physics.

Generally, the assemblies typically used in introductory physics laboratory courses to build an Atwood machine require the use of one or more universal supports. Here, I present an assembly composed entirely of LEGO bricks, as shown in Fig. 2(a). This assembly consists of a structure made up of a set of three LEGO baseplates of 32 × 32 studs with a magnetic sheet attached to the front side. By means of the magnetic sheet, these plates are attached to a blackboard fixed to a wall, as shown in Fig. 2(a). To assemble the pulley, the LEGO Technic Wedge Belt Wheel Pulley is used in conjunction with other LEGO parts¹⁹ [see Fig. 2(c), top]. Once the pulley is assembled, a string is passed through this pulley, and two bodies are attached to each end of this string. At one end, a cart designed entirely with LEGO bricks is attached. A PocketLab Voyager 2 is mounted to the cart to collect the acceleration of the system.²⁰ It is also possible to measure the acceleration of the cart by means of a video camera and then analyze it with software such as Tracker,²¹ or by mounting a smartphone to collect the acceleration by means of its accelerometer.^22,23

The cart rests on a flat surface, composed of 130 LEGO bricks, with approximate dimensions of 1.6 cm thick, 64 cm long, and 5.92 cm wide (2 × 80 × 7.4 in LEGO dimensions). The cart travels along a horizontal path, which is constructed using 26 modified LEGO Plates 1 × 8 with Door Rail. At the other end of the string is hung a LEGO block with dimensions of 4.8 cm wide, 7.2 cm high, and 3.2 cm deep (6 × 9 × 4 in LEGO dimensions). A Bar 6L together with a Round Tile 2 × 2 with Open Stud is attached to the inside of the block, to which metal discs of masses of 0.01 kg each are successively added. Finally, for the demonstration purposes of this article, the experimental results using the LEGO pulley will be contrasted with one that is used in physics laboratories, hereafter referred as the traditional pulley²⁴ [see Fig. 2(c) below].

Guided by Eq. (1), Fig. 3 plots the experimentally measured acceleration of the system as a function of the ratio of the masses of the system.²⁶ The points in red represent the experimental data captured using the LEGO pulley, and those in blue the traditional pulley. A linear trend is observed in the pattern of the data, which is consistent with what is expected according to the theoretical model. The red and blue lines represent the linear fits for the respective cases. When extracting the slope of the linear fit, results close to the accepted g (9.78 m/s²) are observed, obtaining an estimated value for g equivalent to 9.68 m/s² when using the LEGO pulley, and a value of 9.76 m/s² when using the traditional pulley. The above yields a relative percentage error equivalent to 1% and 0.2% when compared with the accepted value of g. The theoretical model proposed here to interpret the experimental results assumes the absence of friction. While this simplification may overlook certain complexities, the results appear to align favorably. Nevertheless, in the event of exploring the impact of friction, it is possible to incorporate the effects of friction, both between the pulley during rotation and between the cart and the rail, into the analysis.

The above results demonstrate that it is possible to use the LEGO system for experimental physics studies addressed in introductory courses. At the same time, LEGO bricks offer high flexibility to test other variations of the Atwood machine, such as tilting the surface on which the carriage slides, implementing a system of several pulleys, or some other variation presented in Ref. 18.

Here I consider a system of two LEGO carts of mass M = 0.0434 kg each moving over a horizontal path composed of 24 modified LEGO Plates 1 × 8 with Door Rail. Due to the special type of plate, the carts’ motion takes place only along the horizontal path. The two carts are attached to springs with constant κ = 11.5 N/m. Each spring is attached to each LEGO cart through a Technic pin junction (a Pin with Friction Ridges and Tow Ball with Squared Pin Hole). To prevent the carts from jumping over the horizontal surface, I attached two 0.01-kg masses to each of them. The system is shown in Fig. 4 (top).

This system is known to have two normal modes of oscillation: the symmetric and the antisymmetric mode. Figure 4 (left) shows the results obtained experimentally for both modes. The initial conditions are shown in phase (top left) and out of phase (bottom left), and on the left, the variation of the position over time (during ~3 s) of both carts are shown in red and green. Each point represents the position of the carts every 0.04 s. For the construction of these graphs, the dynamics of the carts were recorded using the camera of an iPhone SE at 240 frames/s and then tracked using the Tracker software.²¹ The positions of the carts were taken every 10 frames and then approximated to the nearest integer. As a result, the plots of position over time were obtained as shown in Fig. 4. Although the presence of friction in the system is observed, both oscillation modes are captured using the discrete grid of the LEGO system. Finally, an example of a case involving the superposition of both symmetric and antisymmetric modes is shown in Fig. 4 (lower right), showing the potential of LEGO bricks to capture oscillatory dynamics.

This type of physics phenomenon reflects the full potential of LEGO bricks for modeling in physics. As in traditional electromagnetics laboratories, the mapping of electrical potential is done by using graphite paper or a tank with water, which has a paper grid attached to the bottom of it. This system has conductive electrodes (which can vary in geometry), which are connected to a continuous voltage source. In this instance, a LEGO grid of dimensions 30 × 30 will be used, on which water will be added. Here I highlight the advantage of the typical LEGO grid in that it offers the possibility of assembling different electrode configurations with a high level of flexibility. At the same time, the LEGO grid also offers a straightforward way to proceed with the spatial mapping of the electric potential (in this case, in a Cartesian way along the horizontal and vertical directions). Depending on the type of charge distribution and its geometrical arrangements, it is possible to use a 1 × 1 round LEGO tile to define specific regions for mapping the electric potential, either using one type of polar coordinates for circular charge distributions or another type of curvilinear coordinates for more complex configurations. Finally, the LEGO grid was inserted inside a rectangular acrylic support with a depth of 2 cm to prevent water from leaking through the edges of the grid.

In this case, I will use as an example the mapping of the electric potential of two-point charges.²⁷ In doing so, I used two Round 2 × 2 Tiles with Bottom Stud Holder as geometries for conductors, which are inserted in the central region of the grid toward the edges [see Figs. 5(a) and (b)]. For these LEGO rounds to conduct electricity, a conductive adhesive tape is attached to them, as shown in the lower part of Fig. 5. Once conductive adhesive tapes are attached to the round LEGO tiles, each free end of the tape is connected to a 10-V DC voltage source. The system is then filled with water to a height of approximately 1 cm (slightly more than the height of a 1 × 1 LEGO brick). The electrical potential is then mapped with a voltmeter along the horizontal and vertical axes. The results are shown in Fig. 5(c). In the center of the figure, the equipotential curves are shown using LEGO plates, and at the top, the electric potential is represented in its three-dimensional form. In this case, each value of the electric potential measured for each LEGO grid point functions as a geometric site to represent the electric potential. In case there is not enough time for the experimental measurement of the potential, this type of representation can also be made by using theoretical data or can be complemented by using a PhET simulation.²⁸ In this sense, the use of LEGO bricks allows for scaffolding the modeling of the electric potential from its two-dimensional and three-dimensional representation.

The contribution of this article is to present the use of LEGO bricks as a system that facilitates modeling in physics, which can be implemented either as demonstrative activities in the classroom or as laboratory activities [Ref. 29, pp. 279–281]. In this regard, the demonstrative examples presented in this article correspond to an extension and deepening of the use of LEGO bricks in the field of physics with a pedagogical purpose. For example, the demonstrative cases presented in this article can be implemented as forms of inquiry for the promotion of physical concepts, to promote critical thinking, to develop the ability to represent in multiple ways, or to promote creativity. In addition, these activities can be completed with simulations, such as PhET simulations. Although the implementation of these activities using LEGO bricks can be challenging or time consuming for implementation, the use of LEGO bricks has a high pedagogical value for scaffolding modeling processes in physics, as it requires students to be involved both cognitively and bodily.³⁰ Having said this, more empirical research is needed to study the impact of the presented activities based on LEGO bricks in the promotion of learning as pedagogic activities in laboratory settings. To this end, what is presented in this article only represents the initial point of research that has the purpose in the short and medium term to present evidence on the impact on learning in the use of LEGO bricks in introductory physics laboratory courses.

I appreciate the constant support, motivation, and suggestions of Dr. Yaegan Doran, Mr. Maximiliano Zorondo, and Dr. Alessandra Diaz. This article is not funded or sponsored by the LEGO company. For the creation of the digital figures, the software Studio version 2.22.12, and Part Designer version 2.22.4 were used together with the software Tracker version 6.1.1.

Dany López González earned a master’s degree in physics from the University of Chile and holds a PhD in education from both the Pontifical Catholic University of Chile and the Australian Catholic University. His research interests focus on physics education and the role of multimodal language for modeling in physics. dxlopez@uc.cl