Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: myuncle on 07/04/2023 11:34:55
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I am asking this because I have never tried, it's hard to find a cassette player now. But I was thinking that when we were playing a cassette inside a fast moving car, the speed of the tape would be considered faster only for those outside the car, but for those inside the car the speed of the casstte would be totally normal and the speed of sound would be totally normal because the air is contained and travelling within the car. The same could be said for any spinning things, examples, a drill, a fan or a turntable inside the ISS for us on Earth would be spinning much faster, because we add the speed of the ISS to it, but for those inside the ISS the drill speed is normal, and the turntable speed is the same normal speed, with a normal sound. But let's say I am in my room, I have a cassette player (I don't... ;D) with blue tooth speakers (so the speakers are not moving), and I spin the cassette around me with a rope: in this case, should I add the rope speed to the cassette speed, should I hear a different sound, or will I hear a normal sound without any acceleration?
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The speed of the tape only matters relative to the magnetic head that senses the tape as it moves across. So spinning the wheels of the cassette faster to make the tape wind faster will change the pitch of the sound, but hurling the whole tape player around the room won't change anything.
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The speed of the tape only matters relative to the magnetic head that senses the tape as it moves across. So spinning the wheels of the cassette faster to make the tape wind faster will change the pitch of the sound, but hurling the whole tape player around the room won't change anything.
True, makes sense. And the same could be said for a drill used in the ISS, the speed relative to its shaft doesn't change.
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Spinning a cassette player with a rope: same sound?
If your cassette player has a large speaker at each end, and the rope is attached in the middle...
- Then as the cassette player spins on the end of the rope, one speaker will be moving towards you, and one will be moving away
- Producing equal and opposite Doppler shifts from each speaker as the rope spins.
- A form of frequency distortion...
The fact that the speakers are usually on just one side of the cassette play will add amplitude modulation, perhaps a bit like the Leslie Speaker...
https://en.wikipedia.org/wiki/Leslie_speaker