The Whistle and the Funnel
You will need: A whistle, funnel, string.
Whirl this equipment in a circle and the whistle will blow a note. The air which is forced through the funnel into the whistle causes it to blow.
Now let a friend swing the funnel horizontally while you stand to one side so that the whistle first approaches and then retreats from you on its circular course.
In your position, the note from the whistle will seem to rise and falls like a siren. (This is called 'Doppler's effect.')
Your friend, however, will hear only one tone.
Children learn best through doing
Before children can understand a thing, they need experience: seeing, touching, hearing, tasting, smelling; choosing, arranging, putting things together, taking things apart. Experimenting with real things.
Old-time school teaching used only words and the teachers thought children knew something if they could repeat it. Now we know better. To reach practical understanding we do not need to use many words with young children.
Children are clever. They learn a lot, without being taught. The greatest skill - to be able to talk, to communicate is learnt outside school. In the classroom it's the children who need to talk the most. Unfortunately it is the teacher who does most of the talking!