OK, the Kid Down The Street came to me with a project. He has to make something with all SIX(!) simple machines.
So, I said to him, "There are only THREE simple machines. The lever, the wheel and the inclined plane."
"No," he said, "there are SIX simple machines. The lever, the wheel and axle, the wedge, the pulley, the screw and the inclined plane."
"Bullshit!" says I, "A pulley is just a wheel (and maybe, when you add in a rope, it's got a little lever mixed in), a wedge is just an inclined plane and a screw is just an inclined plane wrapped around a wheel."
"Look it up." says the Smart Ass Down The Street.
So, I googled "Simple Machines" and, lo and behold, it appears that they are teaching kids about these SIX things - the original three plus the three inbred cousins.
What the f*ck?