Two issues with this that I see - the vibration a string could demonstrate would have to be a latitudinal motion whereas a longitudinal motion would need a weight on a spring. The second thing I see is that the length of the string and weight would have to be tuned to the same rate of motion, whether a string or a spring. If you swing a weight back and forth at a faster rate than the weight can move it can be possible to move the hanging point back and forth fast enough that the weight hardly moves. But if you swing it one way slowly then back the other way you can get the weight to swing far more than the motion you put into it.

On a spring & weight, the amount of weight and strength of the spring also need to match the frequency of the vibrations. All of that requires some real numbers. The TS is only looking for a visual proof that shaking is occurring.

Hi,

Sure, and I gave the actual application. It was mostly a back and forth horizontal motion that almost any string and weight could show. Of course the string can't be 1 inch long, I think mine was at least a yard or two.
If it doesn't show any motion, change the length
I had another string for an indication of fan operation. Smoke works even better though for really gentle breezes.

I can think of an interesting spring for this, a Slinky (ha ha).

 

a Slinky

Not a bad idea. Best of both worlds. And given the length of the slinky, there could be many harmonic vibrations the slinky could match up with.

 

Not a bad idea. Best of both worlds. And given the length of the slinky, there could be many harmonic vibrations the slinky could match up with.

Ha ha, and the funny thing is, I just bought one a few months ago just for the fun of it. They are pretty amazing to examine, and surprisingly well made.
Also amazing is that they are still sold worldwide, something like 250k units per year. Over the years I have read more than 300 million sold. Such a simple thing too.
Also from what I had read, the Super Bowl got its name from a child's toy also. It may be hard to figure out which one without looking it up.