Tuesday, 15 April 2025

Sci: Resonant pendula

There is no such thing as "a pendula". Scientists are typically educated enough to knoe that where in English, the plural form is usually made by adding 's', the ancient Romans spoke Latin, and had different rules for plurals. One pendulum, two pendula, got it? So if you like, we could say resonant pendulums, but not if you're a scientist!

You will need two supports that will hold up a horizontal slack string (kitchen chairs are good supports), several lengths of string, and two heavy masses like large nuts.



Resonant pendula: work out what the name means!

Tie the masses to the loose horizontal line with identical lengths of string. Set one pendulum swinging, and watch what happens after a few swings. Next, remove one mass, add a longer string, and try it again. Is there a transfer of movement when the lengths are different? When the masses are different? When there are several masses hanging on the one system?

Energy is transferred from one pendulum to the other, and then back again, if the strings are the same length. I have never tried this, but I have been told that a pendulum should influence one a quarter of its length (i.e., with half the period), but there should not be the chance to “return the compliment”. Play with it!

(Working like a scientist means making up your own questions, and answering them!

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