Maths question

[lonelybrit]

I'm hoping someone here remembers their A-level-ish maths. Specifically pulleys - since my mind's gone blank and I have no books with me.

So you throw a light inextensible string over a smooth pulley, and yank on it - and you can pull with your entire bodyweight.

If the string then goes over two smooth pulleys, you can effectively pull with twice your body weight. (This ringing any bells? Is this correct?)

So if you have three pulleys then presumably you can effectively pull with a force three times your bodyweight, and because there's no friction etc, this will be true no matter how far apart the pulleys are or where they are in relation to each other? Anyone?

Comments

[that_mireille]

Assuming the ideal frictionless pulley system, it appears you're right.

[lonelybrit]

Ah, wikipedia saves the day again! Thank you, that was the kind of thing I was after exactly! :)

[that_mireille]

It's very handy to find backup for something you *think* you know. (I thought that was it, but that's more basic physics and less pure maths, and I'm *not* an applied-maths sort of person.)

[lonelybrit]

Nah, that was pretty much it. Three pulley's, some wires, some weights and a patient having traction applied. But it's worth seven marks and the two line answer is looking rather forlorn, LOL!