Rolling ball

In this exercise the rolling ball practical will be simulated using Algodoo. Either follow instructions on this page or watch the screen cast at the bottom of the page.

Downloading Algodoo

You can download Algodoo free here. Once you have installed the program then the best way to find out how to use it is to play. To make life easier for this exercise I have made instructions but you may want to ignore them and just try making an inclined ramp with a ball rolling down it.

Note: These instructions are for an older version of the program however the tools are the same.

Making the ground

You can perform simulations in space but to make a ball roll down a slope we need gravity so the first step is to create the Earth. To do this click the plane tool pointed out below. The click half way down the window and holding your finger on the mouse button move the mouse until the ground is horizontal with the arrow up.

Drawing the incline

To draw the plane you use the polygon tool. Once clicked you can draw any shape but you want a triangle. To draw straight lines hold in the shift key draw a line, release shift and press again for the next side of the polygon.

Don’t overlap the triangle with the ground. You can actually leave a gap, it will close when you run the animation.

Drawing the ball

Use the circle creation tool to draw a ball just above the incline.

Running the simulation

To run the simulation simply press the forwards arrow. You can put the ball back up the slope by clicking the move tool and then drag and dropping the ball to where you want it. You don’t have to stop the animation to do this.

Measuring velocity and height

You can measure any quantity related to the ball by first clicking it then the show plot button in the side menu. This will open a window of options. Choose time for the x axis and velocity for the y axis. Repeat but this time choose time and y displacement.

Perform at least 5 runs from different heights and use the graphs to find height and v. It is quicker to do this all in one run rather than starting and stopping all the time. Use the data to plot a graph of v² vs h and find a value for g. Help on doing this can be found here but don't bother with the uncertainties.

No friction

The ball can be made frictionless by clicking it and choosing material from the side menu. Repeat the simulation with a frictionless ball.