Optical illusion disc down an inclined plane

Optical illusion disc down an inclined plane

This activity can be used to talk about the force of gravity, inclined planes, and optical illusions.

What you need:

  • 1 cereal box
  • scissors
  • ruler
  • pen or pencil
  • color markers or poster paint
  • small piece of poster board or card stock.
  • masking tape (the wider the better)
  • round lid to trace a circle (of around 3 inches or 7.5 cm)
  • optional: glue and a small piece of white paper
  • What you Need

  • Step #1

    Open all the flaps of the cereal box, so it’s flat. With a ruler, measure the width of the cereal box and mark the middle. Cut it in half lengthwise. To make a slope, take one of the halves, and from the lateral edge of the cereal box measure 4 inches (10 cm)high. Make a mark. Now take the opposite end of the other half of the cereal box. Measure 1.5 inches (or 3.5 cm) and make a mark.

  • Step #2

    Put the two halves of the box side by side. Make a mark on both sides at a height where the two halves will measure the same (for example, 3 inches or 7.5 cm).

  • Step #3

    Using the ruler, draw a line that joins the mark at one end of the box half (the mark at 4 inches or10 cm), with the mark at the other end (3 inches or 7.5 cm). Do the same with the other half of the box.

  • Step #4

    Cut along those lines.

  • Step #5

    Using masking tape, joint the two halves of the box in the middle. Use tape to hold the flaps of the box in place again. Decorate the outside of your ramp with paints or markers.

  • Step #6

    Use the lid to trace a circle on poster board or card stock. Cut the circle out.

  • Step #7

    Use a pencil or pen to make a round mark 1 inch or 2.5 from the edge of the posterboard circle. This mark will not be in the center of circle.

  • Step #8

    Use a pencil or pen to punch a hole throught the mark you made on the posterboard.

  • Step #9


    Using markers or paint, draw an optical illusion pattern inside the circle. One option is to draw a spiral inside the circle and then use a different color to fill in the white spaces between the lines of this spiral. On the other side of the circle, draw a different pattern with contrasting lines. Depending of the type of poster board you’re suing , you may need to draw it on a circle of white paper, and then glue it to the backside of the cardboard. You can search on the Internet for “optical illusion spin tops” and find other patterns you can copy.

  • Step #10

    Push a pencil through your painted circle, so that the poster board is right in the middle of the pencil.

  • Step #11

    Tape a popsicle stick (or anything similar that will help to stop the rolling pencil) to the lower end of your cardboard slope.

  • Step #12

    Put the pencil across the top of your ramp, and push the circle down the ramp. Watch the effect of your circle’s pattern as it turns round and round, down the ramp.