Here's a sketch of a pulley system that achieves the desired movement:
Components:
* Fixed Pulley: A pulley attached to a stationary point (ceiling, wall, etc.).
* Movable Pulley: A pulley attached to the load.
* Rope: A continuous rope running through the pulleys.
Setup:
1. Attach one end of the rope to the ceiling (or a fixed point).
2. Pass the rope through the fixed pulley.
3. Pass the rope over the movable pulley attached to the load.
4. Pass the rope through the fixed pulley again.
5. Hold the free end of the rope to apply the force.
Movement:
* Pulling the rope 120 cm downwards will result in the movable pulley rising 60 cm.
* Since the load is attached to the movable pulley, it will also rise 60 cm.
* However, the load is attached to the movable pulley with a rope that is twice as long as the distance the movable pulley travels.
* Therefore, the load will only move 20 cm (60 cm / 3).
Diagram:
```
______
/ \
/ \
/ \ -- Fixed Pulley
/____________\
| |
| |
| Load | -- Movable Pulley
| |
| |
| |
| |
| |
/------------\
\ Rope /
\--------/
|
|
|
Applied Force
```
Explanation:
This system utilizes the principle of mechanical advantage. The movable pulley essentially divides the load into two parts, requiring half the force to lift the same weight. However, the tradeoff is that you have to pull the rope twice the distance. In this case, the load moves a third of the distance the applied force travels, achieving the desired 120 cm to 20 cm ratio.
