Algodoo is a physics based 2D sandbox freeware from Algoryx Simulation AB. If you can draw in "paint"  you can make simulations in Algodoo. If you remember "interactive physics" then it's like that but much better and more colourful. I'm a big fan and have been promoting its use for many years. When I was teaching from the front using a SMART board I would use it almost every lesson to add movement to my drawings. It works great with a SMART board, different coloured pens have different functions. I would always construct the simulations in front of the class so they would see how they work but this takes practice, you have to be fast. Now my students make their own simulations. They start by following my instructions but after a while I expect them to be able to work out how to do it alone. It's a fantastic tool for using in an individual investigation, not to replace real practical work but to see what the ideal situation looks like. For example they can launch a projectile with no air resistance then compare it to the situation with air resistance. In this way they can see if air resistance is the reason why their results differ from expected.

Note that I use animated gifs on this page and in many student activities and multiple choice questions. I make these using the advanced export feature in Camtasia. If you want to use any of these gifs in your activities you can simply save my images on your desktop and do what you want with them.


Constant acceleration

Note that the displacement starts at about -10 m, if you want to start at 0 m you need to find the origin, to do this display the grid and look for the bold line.

Free fall

With and without air resistance. Make the ball bigger and air resistance increases. There is also buoyancy.

Projectile motion

Here there is no air resistance. The components of velocity are displayed showing that the horizontal component is constant.

Here a comparison is made between balls of equal mass but different diameter with air resistance. The balls do not interact with each other, this is done by setting "collision layers".


Display forces. You don't have to display them all. the normal force always has two points of action when acting on a block. Some times forces are too small to see so you can change the scale in the visualisation menu top right. This is also where you have all the options for what to display and how to label.

Take components. Here I have hidden the thruster by making it transparent, this is a useful trick.

Students always find the idea that friction between road an tyre is responsible for accelerating a car forwards, well you can see it in Algodoo. The car is a bit of clip art dragged into Algodoo from my desk top.

Energy. You can plot energies in graphs or view snapshots in info. To keep the info or any other pop up open you simply drag it to one side.

Momentum. Perfectly elastic, sticky bodies and explosions. Explosions can either use springs or make the gravitational constant negative and bodies will fly apart. Snap to grid will keep collisions 1 dimensional.

More fun with cars? The car is cut into pieces and all the pieces given the same velocity, no gravity.

Circular motion

Remove gravity and observe the simple case on a mass on a string.

Switch on gravity and see the not so simple case. Switch on air resistance and observe the minimum speed required to complete a circle.

Orbits are easy using the send body into orbit button but don't tell the students about that, get them to calculate the speed required setting G = 1 makes the calculation easy. Notice the movement of the large mass. Try throwing a mass into orbit on your SMART board, it takes some practice but is cool when you manage it.

Modelling tides is fun, see how the moon loses energy.

Simple harmonic motion

To make a perfect pendulum it's best to use a solid bar rather than a string which gives a nice illustration of the way the motion of a real pendulum differs from the theory. You can of course plot displacement, velocity and acceleration against time. If you want students to analyse the data it can be exported to excel. By the way, to get straight strings press shift.

How about trying to recreate one of the old classics like the U tube?


PhET has a great gas simulation but your students will understand it better if they build their own. Gas particles and container are perfectly elastic, no air resistance. Increase temp by increasing speed, measure temp from average KE displayed in info. Pressure is related to weight of piston


Water waves in algodoo are quite beautiful, they even break like waves on a beach. You have to zoom out before constructing to make the water particles small enough.

You can also model standing waves in a string

and sound.  Shows nicely how sound is a compression wave and the molecules do not oscillate but move randomly.


Electric fields can be modelled using gravity, negative charges have +G positive charges have -G. The + and - charges are made in paint.

Electric current can be represented by the flow of water in the usual water analogy.


You can create neat interactive Feynman diagrams. Here I made air resistance very big to stop them wobbling about.

I made this game to show how quarks combine to give mesons and baryons.


Making the material transparent and using lasers opens a whole load of possibilities for optics.


Lenses, made by intersecting two circles.


Rotational mechanics

Balancing torques

Rolling cylinders

Conservation of angular momentum

Fluid flow

Particles of fluid can be tracked by introducing small spheres with the same density as the fluid (this one is faked).


Force an oscillating system at different frequencies.


Alice's adventures in Algodoo land.

Show the equivalence of accelerating systems and gravitational fields.

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