# Thread: Lab equipment mystery device...

1. My physics teacher found some devices that measure the period/frequency of an object on a spring. The centripetal force is measured in Newtons with a spring scale, then the known mass is spun around it's string, where someone is applying a constant force by twisting the post below. (The mass then spins around its post, stretching the spring mor eor less depending on the centripetal force on it. A stopwatch can be used to measure the period). This force is only what's needed to make the bottom of the mass align with the post (refer to this diagram):

http://img433.imageshack.us/my.php?i...ydeviceka3.png

The point of this query is our teacher only found these and they're basically antiques. He's trying to find a good name for them, and I'm trying to find the original name. Does anyone remember this lab equipment and what its "actual" name is?

2.

3. Torsion Pendulum?

4. It does not look very balanced to me, if the shaft rotates and the 'spring mass' moves away fron the shaft then the counter balance will lose efficiency, you'll then get a wobble and the whole thing will vibrate and the results will be erroneous, unless you can indicate all the moving joints which clarify it's operation.

5. Originally Posted by Megabrain
It does not look very balanced to me, if the shaft rotates and the 'spring mass' moves away fron the shaft then the counter balance will lose efficiency, you'll then get a wobble and the whole thing will vibrate and the results will be erroneous, unless you can indicate all the moving joints which clarify it's operation.
Well, during our lab, we did have to hold onto it because it did get a little unstabalized. However, because we had to adjust the distance the mass was from the axis, the bar was the same length, so the bar's distance was changed as well. Because we were constantly applying a consistent force, it seemed to stabalize. Basically, the moving joint was the bottom of the main bar (right).

But it's really not in proportion, I was just hoping to give a general mind-jogger.

As for a "torsion pendulum", that sure seems like the right track. http://en.wikipedia.org/wiki/Torsional_pendulum . Also: http://en.wikipedia.org/wiki/Torsional_pendulum seems to be more on track.

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