I am a physics teacher, but have found myself teaching engineering. I have come across the following pulley question, and am starting to doubt my own understanding of pulleys !
Until now the rule that mechanical advantage equals 2*no. of moveable pulleys seems to have hold fast, but I am not sure that it works in this case. I am wondering if instead a better rule is that mechanical advantage equals no. of supporting ropes ?
For this particular question, would the no. of ropes supporting the load be three or four ?
I am not sure whether or not to count the far left section where the effort is applied.
Any thoughts on which is the most reliable rule, and how to apply it to this question, would be most gratefully received please. Thank you.