Pulleys: Lifting and Direction Change
A pulley is a wheel on an axle that supports movement and changes the direction of a taut cable. Pulleys are fundamental in lifting heavy loads, applying forces, and transmitting power. They operate on the principle of distributing force over multiple rope segments to reduce the required effort.
Key Points
- A pulley is a simple machine consisting of a wheel with a groove and a rope.
- Fixed pulleys change the direction of force but do not multiply it (IMA = 1).
- Movable pulleys multiply force; the load is supported by multiple strands of the rope (IMA = 2 for a single movable pulley).
- A Block and Tackle is a compound system of fixed and movable pulleys that provides a significant mechanical advantage.
- The Ideal Mechanical Advantage (IMA) of a pulley system is equal to the number of rope segments directly supporting the load.
Formulas & Concepts
Ideal Mechanical Advantage (IMA):IMA = n
n (for IMA):Number of supporting rope segments
Efficiency (η):η = (AMA / IMA) * 100%