In mechanical systems, pulleys play a vital role in reducing effort. When comparing two pulley systems lifting the same 10 kg weight, the key difference lies in how force is distributed.
System 1: Fixed Pulley
The first setup features a fixed pulley. Here, the pulley simply changes the direction of the applied force. While convenient, it doesn’t reduce the actual force needed. You still have to apply the full weight’s force to lift it.
Weight = 10 kg
Force required ≈ 98 Newtons (10 kg × 9.8 m/s²)
Advantage: Direction change only
System 2: Movable Pulley
The second system shows a movable pulley attached directly to the weight. This changes everything. A movable pulley cuts the force needed by half because the weight is shared between two rope segments.
Weight = 10 kg
Force required ≈ 49 Newtons
Advantage: Reduced force, easier lifting
Why System 2 Wins
System 2 clearly requires less force. The mechanical advantage of a movable pulley makes lifting the same load significantly easier. This setup doesn’t just change direction—it reduces effort.
Force Efficiency Comparison
| Pulley Type | Force Required | Mechanical Advantage |
|---|---|---|
| Fixed Pulley | ~98 N | 1:1 |
| Movable Pulley | ~49 N | 2:1 |
Movable pulleys are found in cranes, elevators, and construction hoists. Fixed pulleys, while useful for redirection, do not reduce the force needed. That’s why engineers choose based on task efficiency.
Choosing the Right Pulley System
If your goal is to reduce physical effort, a movable pulley is the clear choice. It cuts the required input in half. On the other hand, fixed pulleys are best when the direction of force is your only concern.
Simple Trick to Remember
Fixed pulley = same effort
Movable pulley = less effort
