Tuning fork and measuring cylinders

[dime]

Does anyone do the tuning fork and 250ml measuring cylinder prac as in Science Focus 1 page 145? It is just that to start with I only have 500ml glass measuring cylinders, and one always gets broken. It shouldn't but it does. Having just read the prac in the book, I was wondering if plastic ones could be used. I'd always assumed that glass ones were needed, but the book doesn't say so. I was also wondering if the 100ml plastic ones that are already in the laboratory would suffice. Just wondering what you guys do?

[smiley]

What about old school gas jars? They're a bit more robust.

[dime]

Good thought Smiley. They're not as tall obviously, but would serve the purpose probably. Thanks

[JudyM]

I don't think plastic measuring cylinders will work, but you could try them out first.
perhaps if you use the tallest gas jars you have you might be able to get a result.

[bunsen]

Not sure of your actual prac, but can I assume you are adding water slowly to the cylinder while holding a tuning fork above it?
If so we do something similar here. We use a bucket of water and a"resonance tube", which is a 35cm piece of plastic downpipe.The pipe is raised and lowered in the bucket of water while the tuning fork is vibrating above the pipe. I have markings on the side of pipe indicating length which will match the frequency of different tuning forks. Being able to raise and lower the pipe makes finding the right length easier.
Can also use this technique to tune your didgeridoo or home made pipe organ?

[Loopy]

Hi Dime,
I had a look at the prac, we don't do it here. I suppose it is because of breakage. I reckon if you hit the bench rather than the measuring cylinder breakage will decrease tho. I sincerely question the logic of the writers thinking the little cherubs won't hit a glass measuring cyclinder with a tuning fork hard enough to break it! But I am just a lowly rung in the erudite ladder....

[dime]

Hi Loopy
I totally agree with you. So many of the pracs in books are actually impractical with students. I think I might just say in future a no to that prac.
Hi Bunsen
That is exactly the prac. I might investigate making the resonance tube like yours as it would be good for a demo. Mind you if you get a result with a plastic downpipe, maybe plastic measuring cylinders will work. I think I should do some experimenting, when I've got nothing better to do. Haha,
Thanks all for your input, have a good break everyone.

[DavidPeterson]

We use PVC piping and buckets as well....

[smiley]

I just gave it a try with a piece of PVC pipe, and a 500mL plastic measuring cylinder. There was a definite "Sweet spot". Here's what I did:

Fill a 500mL cylinder all the way to the top. Drop a 500cm piece of pipe into the cylinder. Strike the tuning fork on a rubber bung and hold it over the pipe. Hold your ear over both, and raise the pipe until you hear a tonal change. With a bit of practice you can clearly identify the spot where the sound is clearest.

[macca]

I like to pick out a few precious cherubs have them come to the front of the class, have a large watch glass filled with water tell them they need to get real close as in 6" from it so they can hear it. Then hit the turning fork on the bench and place vertically above the watch glass, tends to make the make-up run.