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### Easter fun!

Just a quick post to show you some of the fun stuff I got up to over Easter weekend. Here is the miniature Trebuchet my brother and I made out of just Easter egg boxes, string, cups, and a pencil. 😀 It totally demolishes the cardboard castle we made!

trebuchet

*Problems with video right now – I will update later but here is a picture*

The trebuchet in action!

We always make something at Easter!

The yoyo

I also went to a friend’s fancy dress party, and whilst there, a man dressed as a scottish warrior made a yoyo out of party rings for me to do a demonstration with.

Nico (software engineer and maker of party-ring yoyos!

Thanks, Nico!

To explain, the demonstration involves guessing which way the yoyo will roll (if at all) when rolled up a certain way.

This is something that defies instinct (it turns out even drunk physicists get it wrong!) but physics tells us that the rotation (assuming friction on the surface) depends only on the direction of the force, and its position with respect to the point of contact on the surface. Whichever way round you roll it, if you pull towards you, it rolls towards you, because the force is applied above the point of contact with the table.

For this reason, my giant yoyo with a sidebar (see “Poisson d’Avril and Poisson Statistics”) rolls the other way if you apply the force from the bottom (below the table).

As a bee, I explain the rotation of a yoyo to a viking physicist

Anyway, I hope you enjoy the silly pictures!