TOK physics: Green boxes

Knowledge questions

Are some types of knowledge more useful than others?

How can we know that current knowledge is an improvement upon past knowledge?

What counts as a good justification for a claim?

How important are material tools in the production or acquisition of knowledge?

What role does imagination play in producing knowledge about the world?

This is a virtual version of the classic "what is inside the black box" problem. To do this activity you will need to instal Algodoo on your computer, this is free and can be downloaded from here.

Once you have installed Algodoo, download and open this 4 green boxes. but don't start playing with it until you have read below.

You have to find out what is in the boxes without opening them. Box A is empty.

  • Press the arrow to play
  • The hand tool is used to move them around. You are only allowed to use this tool. Maybe you are already an Algodoo expert having used it in physics but you are not allowed to use other tools. The reason is that you might reveal the inside by accident. If you want to reset press the back arrow.


Try playing with the boxes to see if you can work out what's inside. Keep the simulation running all the time, if you stop the simulation and move the box the contents will be left behind.

It's not easy but here is some physics to help:

  • When a pendulum is at rest, its centre of mass always hangs directly below the pivot.
  • The time period of a pendulum is related to the distance from pivot to centre of mass, a short pendulum swings faster.

  • Try swinging the box by different corners and sides.
  • You can also try rolling the boxes, they will roll over when the centre of mass is over the corner.

When you have formulated a hypothesis you can try passing a laser through each box, the laser passes through the box but reflects off the object inside.

Got it now?

Do your findings support your hypothesis? If not, try to explain the way the boxes swing using your knew evidence.

Click the box and press delete to see inside. Were you right?

Wondering how swinging the boxes can reveal the contents?

Box A has the same time period when hung from each corner. If held from the centre it spins round. If held from the middle of an edge it rests with the lower edge parallel to the ground.

Box B hangs so that the centre of the box is not below the pivot, the centre of mass is lower than the centre when pivoted from a top corner but above centre when pivoted from a bottom corner. If held from the centre of an edge the bottom always hanging down. If held from the centre the bottom is always down.The time period of the oscillation is also shorter when swung from one of the bottom corners.

Box C always hangs so the centre of mass is below the centre, the time period of the oscillations is also the same for the top and bottom corners. If held from the centre the bottom is sometimes down and sometimes the top is down.

Box D always hangs with the centre below the pivot, the mass could be in the centre, however if you pivot it from the centre of a side it hangs to the left or right, the mass inside is moving. If held from the centre one corner is always down but which corner is random.

Would it have been easier if you could pick up the boxes? What additional information would you have?
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