Question

find the mechanical advantage

Answer 1

Isn't it the force that's output divided by force input?

Answer 2

you pull the rope on right side to lift the bottom block...

Answer 3

Yes @the_destroyer ..

Answer 4

Looks i need to find the ratio of `output force` and the `weight of block`

Answer 5

Then do it.

Answer 6

all ropes and pulleys are massless. the tension in the rightmost pulley's rope = F. the tension in the middle pulley's rope = 2F (since the pulley is massless too and can't have a net force) and in the last pulley's rope, it's = 4F.

so just exerting a force of F on the first rope exerts a tensile force F + 2F + 4F = 7F on the block.

Answer 7

mechanical advantage is 7 is it ?

Answer 8

I think so. This is the first time I've encountered a problem like this.

Answer 9

me too..
how did you get the idea that starting from right side gives the answer smoothly ?

Answer 10

you can just make equations and solve it, but looking at it that way (like falling dominoes) gives you a nice, intuitive feel for the whole situation