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When a person blows into one end of a long pipe, creating a high-pressure air pulse that moves through it, what happens when this pulse reaches the opposite end of the pipe?
- A high-pressure pulse begins moving back through the pipe if the far end is open.
- A low-pressure pulse begins moving back through the pipe if the far end is open.
- A low-pressure pulse begins moving back through the pipe if the far end is closed.
- A high-pressure pulse begins moving back through the pipe if the far end is closed.
Correct answer: A low-pressure pulse begins moving back through the pipe if the far end is open.
Solution
A high-pressure (compression) pulse reaching the OPEN end of a pipe reflects as a low-pressure (rarefaction) pulse, since an open end is a pressure node. So a low-pressure pulse travels back if the far end is open (option index 1). The stored answer (index 2) wrongly requires a closed end.
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