Open source software has always been a cornerstone in scientific applications. From supercomputers to CERN labs, handling some of the greatest discoveries of humankind and accelerating particles beyond imagination, open source software has provided the framework for all necessary technological usage. Bringing it down to a simpler level, KDE's Step provides you a platform to test out some of the most important basic concepts in physics, like simple motion, electrostatics and gravitation, and even things like spring (harmonic) motion. Developing an intuition about these phenomena can finally bridge the knowledge gap that students need. So if you are a physics teacher (or student), KDE Step is worth your attention.Interface and ExperienceUsing the basic KDE design kit, the application looks quite familiar as it is. It is arranged in a very efficient manner, with all the usable objects on a panel on the left side of the window, while the right side holds the panel that can be used to modify any of the attributes of those objects as well as a panel that shows the history of the steps (no pun intended) made by the user. On the top of the window, all the menus are present with the undo/redo buttons, and most importantly, the button that allows you to start the simulation.To demonstrate the elements and how they're used in the best way possible, I'm going to show different simulations that incorporate said elements. It is the most efficient and vivid way, since it is, after all, a simulation app.Simple Harmonic MotionAs a very famous quote from Sidney Coleman says, "The career of a young theoretical physicist consists of treating the harmonic oscillator in ever-increasing levels of abstraction." Keeping up with that sentiment, I will show a very basic demonstration of a simple harmonic motion. 0:00 /0:16 1× Simple Harmonic Motion The elements used here are two particles, a spring, a graph, weight field and an anchor. Particles in Step are simple zero-dimensional point objects with modifiable position, color, velocity, mass, momentum and kinetic energy. Springs are simple, you can attach both ends to objects, you can change the stiffness. Anchors are utilities that can be used to fix the position of an object to the scene. No matter what, it will not move from where it is placed. A weight field simply simulates the gravitational force of earth for all the objects placed on the scene, but again, you can modify the gravitational acceleration to suit whatever kind of simulation you're trying to run (for example, trying to simulate the gravitational force on the moon). Finally, the graph utility can be used to plot any property of any object on the scene against any other property.Soft BodyWhile sounding like a promise made by a moisturizer, soft body is not that but a category of objects in physics that are not rigid but that deform and change shape according to the parameters set. More accurate, and as shown in the app itself, it can be thought of as an object made of small particles connected to each other by springs that deform according to the force provided. 0:00 /0:09 1× Soft body simulation Two new elements are used here, a soft body (that has already been described) and a box. A box is just that, a rectangle with modifiable dimensions, where apart from what you can already change in a particle, you can also change the angular velocity, angular momentum, inertia, and so on.📋If you're wondering why the soft body falls on the left even though it has been placed centrally on the screen, that is because nothing can be truly zero in this context. There's always a miniscule value left, and in this case, even when the value is defined as 0, it is some exponentially small value close to it on the left (negative).OrbitAnother basic simulation that can really help is that of an orbit. Step provides a gravitational field simulation, in which the universal law of gravitation starts holding true and applying within the canvas. In this simulation, I've modified the value of the gravitational constant to something that allows my particle to orbit the central particle (because I finally can), and I'm using a controller to change the mass of my central particle while the simulation is going on to show how that changes the velocity and distance of the revolving particle. 0:00 /0:31 1× Orbit simulation As you can see, for the first part of the video, it is making a calm orbit but as soon as I start increasing the mass, the particle comes closer (as one would expect) and when I decrease it, the particle goes out the frame (a little dramatic, but still expected).Compound PendulumHave you ever wondered what an oscillating lambda would look like? Well wonder no further because Step allows you to make any kind of polygon that you would like to make with the polygon tool, and then you can use a pin to fix the position of one point in that body to the canvas. And some weight force to the scene, and there you go. A lambda pendulum: 0:00 /0:11 1× Compound pendulum simulation This kind of pendulum that isn't one concentrated mass but distributed instead is called a compound pendulum in physics, which can be quite difficult to visualize sometimes.Linear-Angular ParallelsStudents often struggle with the equations for the motion of a disk, or anything that has to do with rotating rigid bodies, but it is only a matter of translation of the values in the usual linear equations of motion into those that concern rotating bodies. For example, mass gets replaced with moment of inertia, velocity with angular velocity, same with acceleration and so on. In the following simulation, that's exactly what we're showing: 0:00 /0:07 1× Linear-rotating parallels. In this simulation, the particle and the disk have mass and moment of inertia with the value 1, velocity and angular velocity with value 6, acceleration and angular acceleration -2 respectively. As you can see, the changes happen hand-in-hand, making it clear how the equations work practically parallelly. I have used a linear motor to apply a linear force to the particle and a circular motor to apply a torque to the disk. The values on display can be shown using the meter utility.Stable and Unstable Equilibrium PositionsIn the first case, I've fixed two positive charges of equal magnitude on the canvas with anchors. Another positive charge was placed right in between them. The charge, of course, will be in equilibrium just by the virtue of being smackdab right in the middle of the positive charges. What happens if I slightly move the central charge from its position? 0:00 /0:09 1× Stable equilibrium state for charges The charge starts oscillating. In a real life scenario where there are losses due to friction and so on, this will return to the equilibrium position right in the middle. But what if my central charge is negative? What happens then? 0:00 /0:06 1× Unstable equilibrium state for charges As you can see, the charge moves on to the side of movement, as you would expect. In this case, the equilibrium was unstable, meaning even the slight change in position on one side will result in absolute ruin of the equilibrium state. I've used charged particles, which are similar to normal particles but with the added option of adding a charge to them. Similar to how we did with gravitation, you need to add the Coulomb field to the canvas in order for the law of electrostatics to start applying.ConstraintsA lot of basic physics is based on constraints, which can be of different sorts. The most basic one is where the distance between two bodies is fixed, so that the motion of one of the bodies impacts that of the other. So in this simulation, I've done that exactly with a massless stick, which connects two bodies in Step. I've given a certain velocity to one of the particles, and you can see here how it impacts the other one: 0:00 /0:09 1× Usage of stick in Step 📋It is important to note that sometimes the stick doesn't work really well. It is not supposed to be elastic, but it sometimes acts more like a spring than a stick if not configured exactly well.Perfect Gas SimulationFinally, Step has a tool that lets you simulate a perfect gas, following the basic principles of kinetic theory of gases. When applying it on the canvas, you can configure the area that the gas will exist in, the number of particles inside that area, the concentration, the temperature, particle mass and mean velocity. Sure, some of these things are dependent on each other and all of them being configurable individually does seem a little counter-intuitive, but if you change one of the values that another depends upon, it changes automatically. There's no disregard for the physics of it here. 0:00 /0:18 1× 📋The gas particles are not configured to interact with any other bodies or walls/objects in the vicinity. If you put boxes or polygons to see how the gas interacts with them, Step will show an error saying it isn't possible.Wrapping UpThere are some very obvious points at which Step breaks. Not even showing an error, it just breaks. For example, if you configure the mass of a particle to be 0 or very close to it, for any simulation that involves forces or collisions, the canvas just disappears. Obviously, massless particles are not in the scope of scenarios which Step can simulate.Overall, Step has some excellent options that can really help students visualize their physics lesson up to an elementary undergraduate level. As a student of Physics, I have been using it for years to clear my doubts, but it is only obvious that the simulation can only be as helpful and accurate as you are careful with setting it up. More than that, it helps you explore possibilities that aren't possible in the physical world, such as completely ideal conditions of zero friction, the ability to change fundamental and universal constants and so on.On a related note, you may want to check out the list of distros for schools and education.I hope this article was helpful and that you have fun seeing the answers to your physics doubts come to life. Cheers!