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Physics
Pulley lab
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Pull the rope and change the arrangement to explore force, distance and work.
Watch the rope and load move
Pull down to lift the load
Drag the handle in the scene, or use the slider below.
- Required pulling force
- 100 N
- Lift height
- 0 m
- Rope displacement
- 0 m
F = P / 1
1 supporting strands · T = 100 N
The fixed pulley changes the direction of pull. The pulling force equals the load’s weight.
Release the handle to hold the rope.
Explore work
Less force, the same work
- Input work
- 0 J
- Lifting work
- 0 J
A = F × s = P × h
Work done by the pulling force is measured from the starting position. It decreases when lowering; this is not accumulated positive work.
| n | F (N) | s (m) | A (J) |
|---|---|---|---|
| 1 | 100 | 0.5 | 50 |
| 2 | 50 | 1 | 50 |
| 4 | 25 | 2 | 50 |
Model notes
- Quasi-static lifting: the displayed force holds or steadily lifts the load. Acceleration is not modelled.
- The rope is massless, inextensible and taut. Pulleys and hooks are massless and frictionless; supporting strands are vertical.
- We use g = 10 N/kg. The 0 m mark is a suspended position. Releasing the interaction continues holding the rope.
- n counts strands supporting the moving load: F = mg/n, s = nh. A = Fs = mgh is work done by the pulling force from the starting position; it decreases when lowering. Net work by all forces on the load equals its change in kinetic energy, zero during steady lifting. The entire force arrows, including their heads, share a linear length scale.