Why does a police siren change its note as it races past you?
Open for the projector Present it step by step
Classroom mode
A question for the whole room
One story to open. A room full of ideas to test.
Ready in three steps
- Open the story.Read and try the first pages together.
- Pause for a prediction.At the story’s question, read its choices aloud. Invite a vote and ask, “What makes you think that?”
- Run it. Watch. Wonder.Choose the class’s prediction, run the experiment, and compare what happened with your guesses.
Different guesses are welcome. The experiment gives everyone something to rethink.
Something to put on paper
A one-page prediction and observation sheet. No answers included.
After the experiment: discussion notes
Talk about what happened
- Predict first: if the siren drives toward you, will the waves reaching your ear be squished closer together or spread further apart? Then watch and check.
- Why does the pitch drop the exact instant the siren passes you, instead of changing slowly?
- A parked siren and a moving siren both play the same note. Predict which one tells you it just went by, and explain why.
Where it shows up in real life
- An ambulance or police car racing past on the street
- The ice-cream truck or a motorbike zooming by
- A race car or train horn blasting past at a track or crossing
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