Simple Machines

[grayfalcon89]

I'm having a test on this this week and well, I have hard time understanding this concept.

 

#1: With pulleys, my teacher tried to explain that I can find the ideal mechanical advantage of the pulleys by counting the "number" of strands. Can anyone explain how I count the strands? Say in this website:

 

http://www.phys.unsw.edu.au/~jw/blocks.html

 

(i), (ii), (iii) and (iv), are the IMA 1 and 2 for first two? I don't know how to do the 3rd one and I think the last one is 6...

 

Can anyone help me with this? It is so annoying!

 

#2: Bicycles... Can anyone tell me how bicycle breaks down into simple machines?

[swansont]

I'm having a test on this this week and well, I have hard time understanding this concept.

 

#1: With pulleys, my teacher tried to explain that I can find the ideal mechanical advantage of the pulleys by counting the "number" of strands. Can anyone explain how I count the strands? Say in this website:

 

http://www.phys.unsw.edu.au/~jw/blocks.html

 

(i), (ii), (iii) and (iv), are the IMA 1 and 2 for first two? I don't know how to do the 3rd one and I think the last one is 6...

 

Can anyone help me with this? It is so annoying!

 

The explanation and answers are given on that page. You don't count the line on which you are pulling. Each other line that comes after a pulley is a multiplier of mechanical advantage. iii) is 4

[grayfalcon89]

Thank you.

 

What happen if you have the pulley upside down though? Like, here, this is a copy of our lab from Physics class (you can find basically on internet these days)

 

http://weird-science.org/main/res0idt9/sitebuildercontent/sitebuilderfiles/machinewithpulleys.pdf

 

Anyway, on the first page, (2) pulley is just upside down version of simple pulley. My physics teacher and classmate told me that this has IMA of 2. But according to not counting the string you're pulling, this IMA should be 1. So how is this 2?!?