Dr Ian Johnston
speaker
46 appearances
2 recordings
1 series
first heard Nov 2012
last heard Feb 2015
Dr Ian Johnston’s voice in public audio — every appearance, attributed to the second.
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Appearances
That's an interesting question.
I'm just surprised that I couldn't find the answer.
When you first got in touch, my natural response was to say, well, just Google it, crushed strength of a Lego brick, somebody must have done it.
And to my surprise, I found a lot of speculation about what it is, but no clear evidence about what it is.
There are several ways of approaching it, but the way I'm going to do it today is we're going to find what load, what force is required to crush a Lego brick, and then we're going to work out what mass that corresponds to sitting on top of the Lego brick.
A mass is not a force, but a mass produces a force because of gravity.
Once we know that mass, and we know the mass of one Lego brick, we know how many Lego bricks we had to produce the right mass to produce the right force to crush the Lego brick.
This is a server hydraulic testing machine.
There's a hydraulic pump which runs a hydraulic ram, pushing a plate upwards on which we've got a Lego brick sitting.
On top of that, there's another plate with a load cell on top which measures the force on the Lego brick as it's compressed.
And because we're beginning to get a little bit nervous about the number of bits it might fly into when it's failing, we're setting it up to do it automatically so that we can all back out of the room so that none of us is in range when the thing goes bang.
Four and a half kilonewtons.
We're just approaching half a tonne now.
It's hardly increasing anymore.
It's more or less constant.
It means we've probably got a material failure and the material is just flowing out of the way now and not able to take in any more.
Well, anyway, the final result is... The average of the three, which is pretty tightly clustered together, which gives me confidence, is 4,240 newtons.
That's equivalent to a mass on top of the thing of 432 kilograms...
At 1.152 grams per brick, that's 375,000 bricks.
A few more, but we'll ignore that, it's experimental error, giving us a grand total height of 3,591 metres.
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