Determining Pulley Strings: Efficiency & Function Explained

[livvy07]

How do you determine how many strings a pulley has by looking at it?
Like say this picture for example:
http://www.knowledgerush.com/wiki_image/8/8f/Pulley_class2.PNG"
Would that be 2 strings?

And I think the efficiency improves as the number of strings lifting the mass increases? I that correct?

Any help would be greatly appreciated-I'm really confused on pulleys even though these questions seem so easy

 

[Saladsamurai]

I would say that this pulley system has only 1 string. The string that fixes the pulley to the mass does not actually do anything. The mass could just as easily be bolted to the pulley.

The efficiency improves as the number of pulleys increases.

 

[nickjer]

Not exactly sure what you are asking, but as you can see on the pulley system that the single rope wrapped around the pulley has two tensions in the up direction. Therefore they each contribute to half the weight.

If two similar pulleys were each attached to the weight, then their would be 4 upward tensions, and each tension would have a magnitude W/4.