A pulley is a grooved wheel that guides a rope. It helps us lift loads by changing the direction of force or by sharing the load between rope strands.

What is the difference between fixed and movable pulleys?

A fixed pulley stays in place and only changes direction. A movable pulley moves with the load and halves the effort.

What is the mechanical advantage of a pulley system?

It is load ÷ effort. For an ideal pulley system it equals the number of strands holding the moving load.

Pulleys: Fixed, Movable, Pulley Block, Wheel and Axle

A pulley is a grooved wheel that guides a rope. A fixed pulley only changes the direction of the pull. A movable pulley and a pulley block share the load between several rope strands, so effort = load ÷ number of strands, but you pull more rope. The wheel and axle and the inclined plane also trade a longer distance for a smaller force.

Fixed and movable pulleys

A pulley is a small wheel with a groove. A rope runs in the groove. The wheel can spin freely.

Fixed pulley

The wheel is fixed in one place, for example on a beam. You pull the rope down and the load goes up.

Effort = load (no gain in force).
It changes the direction of the force. Pulling down is easier than pulling up, because you can use your body weight.
Rope pulled = height the load rises.

Movable pulley

The wheel moves up with the load. The load hangs from the wheel. One end of the rope is tied to a fixed point.

2 strands of rope hold the load, so each strand carries half.
Effort = load ÷ 2.
To lift the load 1 m, you must pull 2 m of rope.

Rule that works for all: count the rope strands that hold the moving load.

Pulley blocks (combined pulleys)

A pulley block joins fixed and movable pulleys with one long rope. It is also called a block and tackle.

If n strands hold the moving block:

Effort = load ÷ n (ideal, no friction).
Rope pulled = n × height lifted.
Mechanical advantage (MA) = load ÷ effort = n.

The load and the movable pulleys are lifted together, so the weight of the movable block adds to the load in real life. Friction in the wheels adds more. So a real effort is always a bit more than load ÷ n.

Work done by you = effort × rope pulled = load × height (ideal). The machine does not make free work.

Wheel and axle, incline

Wheel and axle

A big wheel is fixed to a small rod called the axle. They turn together. You push the rim of the wheel. The load hangs on the axle rope.

Effort × wheel radius = load × axle radius, so effort = load × axle radius ÷ wheel radius. A bigger wheel gives more help. Examples: steering wheel, door knob, screwdriver, well winch, bicycle pedal and gear.

Inclined plane (ramp)

A ramp lets you raise a load by pushing it along a slope. For no friction:

Effort × ramp length = load × height.

A longer, gentler ramp needs less effort but a longer path. Examples: a ramp to a truck, a mountain road with hairpin bends, a staircase.

All three machines follow one rule: less force, more distance.

Try it: predict, then lift

Open the last 3D step. Set 6 blocks (60 N) and 3 strands. Predict the effort (60 ÷ 3 = 20 N). Then lift the load by 1 m: how long is the rope you pulled? (3 m).

At home

Hang a bag of rice on a spring balance. Lift it straight up and note the reading. Now put a rope over a smooth pencil, or use a toy pulley, and lift again. Try a movable pulley too. Compare the readings and the rope you pulled.

Key formulas and definitions

Fixed pulley: effort = load; rope pulled = height lifted
Pulley system (ideal): effort = load ÷ n, n = strands holding the load
Rope pulled = n × height lifted
Mechanical advantage MA = load ÷ effort (ideal MA = n)
Wheel and axle: effort × wheel radius = load × axle radius
Inclined plane (no friction): effort × length = load × height

Worked examples

1. A fixed pulley lifts a 80 N bucket by 3 m. Find the effort and the rope pulled (ideal).

Fixed pulley: effort = load = 80 N. Rope pulled = height = 3 m.

2. A movable pulley with 2 strands lifts a 120 N load by 2 m. Find the effort and the rope pulled.

Effort = 120 ÷ 2 = 60 N. Rope pulled = 2 × 2 = 4 m. MA = 2.

3. A pulley block has 4 strands holding the load. Find the effort for a 200 N load, and the height lifted when 6 m of rope is pulled.

Effort = 200 ÷ 4 = 50 N. Height = 6 ÷ 4 = 1.5 m.

4. A wheel of radius 0.5 m is fixed to an axle of radius 0.1 m. What effort at the rim lifts a 250 N load?

Effort × 0.5 = 250 × 0.1 = 25, so effort = 50 N. MA = 250 ÷ 50 = 5.

5. You push a 500 N drum up a 5 m long ramp onto a platform 1 m high. What effort is needed (no friction)?

Effort × 5 = 500 × 1, so effort = 100 N. The ramp makes the job 5 times easier, but the path is 5 times longer.

6. A pulley block with 5 strands lifts a 360 N load. A student pulls with 90 N. Find the ideal effort and the efficiency.

Ideal effort = 360 ÷ 5 = 72 N. Efficiency = ideal effort ÷ real effort = 72 ÷ 90 = 0.8, so 80%. (Check: for a 1 m lift, useful work = 360 J, work put in = 90 × 5 = 450 J, and 360 ÷ 450 = 80%.)

Common mistakes

Thinking a fixed pulley reduces the effort. It only changes the direction of the pull.
Counting the wrong strands. Count only the strands that hold the moving block with the load.
Forgetting that more strands means more rope to pull: rope pulled = n × height.
Saying a pulley or ramp saves work. It saves force, but work stays the same (or goes up with friction).

Practice quiz

Practice: answer these yourself

Type or choose your answer, then press Check. Use a hint if you are stuck; the full solution appears after you answer.

Pulleys: How Ropes Make Lifting Easier

🎬 Step-by-step story

🤔 Common doubts, cleared

If a fixed pulley does not reduce the force, why use it?

Which strands do I count?

Effort goes down, so is my work less?

Why does a bigger wheel help?

Is a long ramp really easier?

Is effort always exactly load ÷ n?