Moment of a force

There are 2 NRICH Mathematical resources connected to Moment of a force
Wobbler
problem

Wobbler

Age
16 to 18
Challenge level
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A cone is glued to a hemisphere. When you place it on a table in what position does it come to rest?
Overarch 2
problem

Overarch 2

Age
16 to 18
Challenge level
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Bricks are 20cm long and 10cm high. How high could an arch be built without mortar on a flat horizontal surface, to overhang by 1 metre? How big an overhang is it possible to make like this?