Toys and Physics - Circular motion 2

2.9 Sycamore seed

What happens
This large plastic model of a sycamore seed will 'fly' across the room when the wooden dowel rod is spun between your hands.
Be careful to spin it the right way or else it will fly into your face instead of away from you!

Theory and teaching notes
The plastic seed 'flies' because of its propeller shape. Energy conservation can be demonstrated by spinning it faster – it will fly higher.

2.10 The puzzle of two balls in a plastic holder

What happens
The idea is to get both ball bearings into the depressions at either end of the toy. The only way this can be done is to spin it. The balls "fly out" (actually just try and move in a straight line) and so end up in the depressions.

Theory and teaching notes

2.11 Indoor boomerang

What happens
The polystyrene boomerang should have its arms bent slightly inwards before throwing. It will then return to the thrower. A large hall demonstrates the boomerang principle very well.

Theory and teaching notes
Like the 'real thing' the boomerang is shaped so that the air moves faster over one side of it than the other when it is thrown. This creates a different in pressure and so the boomerang travels in a curved path – hopefully returning to the thrower.
A large hall is the best place to do this.