The Physics of Simulation vs Reality
Summary
If you want a Project Idea with full instructions, please pick one without an asterisk (*) at the end of the title.
Abstract
Science Buddies has many projects where you build something with moving parts or do an experiment with the physics of moving objects. Here are just a few examples, but this is not an exhaustive list! You can search our site to find many more.
- Ball launcher (Figure 1)
- Marble roller coaster (Figure 2)
- Rube Goldberg machine (Figure 3)
- Build A Wall Marble Run (Figure 4)

Figure 1. A catapult-style ball launcher.

Figure 2. A marble roller coaster made from foam pipe insulation.

Figure 3. A Rube Goldberg machine.

Figure 4. A marble run made from cardboard tubes taped to a wall.
You can use a computer program, like Tinkercad Simulab, to simulate the physics involved in many of these projects. Physics simulators help scientists and engineers make predictions about real-world behavior and examine how changing parameters, like dimensions and material properties, can affect the motion of a physical system. Simulations can help save time and reduce the number of physical prototypes you need to build for a project. For example, you could use a simulation to examine the effects of changing the arm length of the ball launcher, the height of the roller coaster loop, the slope of the ramp in the Rube Goldberg machine, or the positions of the cardboard tubes in the marble run. You can use these simulations to help you make informed decisions about your design before building a physical prototype, or before making changes to an existing prototype.
While they are potentially time and cost-saving, you have to be careful when interpreting results from a simulation. It can be difficult to simulate all the intricate details of the real world, like friction between objects, or how exactly two objects will bounce when they collide. The output of the simulation may not perfectly match what happens in the real world, so it can still be important to build and test physical prototypes. You can then compare what happened in the real world to what happened in the simulation, and refine your simulation to improve its accuracy.
For a science project, can you use a physics simulation program and compare the results to a physical experiment? You can choose one of the Science Buddies projects listed above, another one from our site, or come up with your own experiment. Before picking a project, you will need to read the documentation for Simulab (or another simulation program that you choose) and make sure you understand what it can and cannot simulate. For example (as of the time of writing of this project), Tinkercad Simulab can simulate rigid bodies and gravity. This means it will work well for gravity-powered projects like roller coasters or catapults/trebuchets powered by a falling weight. However, it cannot simulate stretchy objects like springs or rubber bands, so would not work for a rubber band-powered catapult.
After you have chosen a project, you will need to set up the real-world experiment and an identical simulation (or at least, a simulation that is as close as possible to the real-world experiment), such as the marble run in Figure 5. Then, compare the behavior of the real-world system with the simulation. For example, for a wall marble run, do the marbles follow the same path in the simulation as they do in the real world? If you adjust the length, spacing, or angle of a section of track in the simulation, can you then use the simulation to predict what will happen if you make the same change to the physical marble run?

Figure 5. The wall marble run from Figure 4 recreated in Tinkercad.
If you do not see the same results, can you identify sources of error that would cause the results to differ? Do the dimensions of the model in your simulation match the real-world dimensions? What about material properties? You can select different materials in Simulab like plastic, rubber, wood, etc., but the material properties might not exactly match the physical materials that you have. Can you make changes to your simulation, your physical experiment, or both to make their results match more closely?
For a more advanced project that requires additional simulation capabilities (springs, air flow, etc.), you will need to look into other software. Some software companies, like Solidworks and Autodesk, offer free or low-cost versions of professional engineering software to students. While more difficult to learn, these programs will offer more simulation capabilities than Tinkercad.
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