Diagrams.ink / Simple machines

Count the strands. Pay in rope.

Choose how many rope segments hold the crate, then drag the red handle down. One continuous rope runs through every pulley, so the strand count sets how much easier the pull gets and how much more rope you must haul.

PULLEYS / IDEAL MODEL
01 — Block and tackle4 supporting segments · ideal advantage × 4
050100LIFT cm050100PULL cmFIXED120 NMOVINGdrag down123456
Fixed pulleysHang from the beam. They only turn the pull downward.
Moving pulleysRide up with the load and add supporting segments.
Supporting segmentsRope strands that pull up on the moving block. Count them.
LoadCrate, 120 N. The green ruler shows its lift.
Your pullRed handle on a spring scale. The red ruler shows rope pulled.
× 4
30 N
0 cm
0.0 cm
Supporting rope segments
Rope at rest100 cm of rope
Drag the red handle, or use the slider. The rope stays where you let go.Ideal model · friction and pulley mass are ignored

Every strand shares the load.

The numbered segments all pull up on the moving block, so each carries an equal share of the crate's 120 N. The free end passes over a fixed pulley, which only turns the rope around, so it carries that same share. A fixed pulley changes direction; each moving pulley adds supporting segments.

pull force F = W / N · ideal MA = N

The price is rope.

To lift the crate by h, every one of the N segments has to get h shorter, so N × h of rope must come out through the free end. The white tape marks sit 20 cm apart along the rope: watch them stream past, fastest in the strand nearest your hand and not at all in a strand tied to the beam. Force down by N, distance up by N, so work in equals work out.

Friction, rope stretch and the mass of the pulleys and rope are ignored. Lengths are illustrative centimetres.

pull distance d = N · h · F·d = W·h