Today I had a gate fitted to my orchard, replacing the scruffy bit of wire netting that had served as the only barrier between my property and the farm animals regularly herded down my road. I am sure my farming neighbours will be pleased. It has rained a lot in the Vendée over the last few months so this bit of ground is very soft. You can see the ruts left by the Land Rover that brought all the equipment in. The trailer sank into the ground and it was quite a palaver getting it out again. I am sure that the ground will grow over again with grass and that everything will be looking lovely by the summer.
To the right you can just see the cement mixer that they used to mix up the concrete needed to hold the gate posts in place. It was electrically powered so we ran a long extension cable down from my kitchen. It draws a fair bit of current so the cable had to be really thick to reduce its resistance. Even copper cable (used in all domestic wiring) has some resistance and 50 metres or so is a long way unless the cable is really thick. Fortunately they had heavy duty extension cables so everything was fine.
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They brought a small digger to level the ground and create a raised pile of earth that I can plant up in due course. He was so good with it – it was just like an extra limb. It was a wonderful demonstration of forces in action. All those levers and hydraulic pistons worked in unison to produce a most animated effect. I want one!
Questions…
- What feature of the digger’s design stopped it from sinking into the soft mud?
- How do you calculate the moment of a force?
- What is ‘the law of balancing beams’?
- How does electrical current change relative to (a) voltage (b) resistance?
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