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Notice what happens to the motion when the sides of the triangle are perpendicular to the floor and plank.
Notice the differences to what happens on the floor and on the plank when the triangle rolls in opposite directions.
You might like to try cutting out a very accurate rolling triangle with which to experiment.
Rolling Triangle
Age 11 to 14
Challenge Level 
Notice what happens to the motion when the sides of the triangle are perpendicular to the floor and plank.
Notice the differences to what happens on the floor and on the plank when the triangle rolls in opposite directions.
You might like to try cutting out a very accurate rolling triangle with which to experiment.
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