In this post, we will discuss three types of pulleys, and how they operate, and how they differ in their operation and utilities. The types we will discuss are *(1) Fixed Pulleys, (2) Movable Pulleys, (3) the Block and Tackle.*

## Fixed Pulleys

A fixed pulley, such as the one in **Figure 1, **is attached to something that doesn’t move, such as a ceiling or wall. A fixed pulley changes only the direction of force, it doesn’t multiply the input force. Hence, the IMA of a fixed pulley is 1.

**Example of a fixed pulley**

Elevator pulley is a fixed pulley – The cable attached to an elevator passes over a fixed pulley at the top of the elevator shaft.

[Read **how pulley is a modified lever**]

## Movable Pulleys

A pulley in which one end of the rope is fixed and the wheel is free to move is called a movable pulley.

*Unlike a fixed pulley, a movable pulley does multiply force.*

Suppose a 4-N weight is hung from the movable pulley in **Figure 2. **The ceiling acts like someone helping you to lift the weight. The rope attached to the ceiling will support half of the weight (2 N here). You need to exert only the other half of the weight (2 N here) – to support and lift the weight.

The output force exerted on the weight is 4 N, and the applied input force is 2 N. Therefore the *IMA *of the movable pulley is 2.

For a fixed pulley, the distance you pull the rope downward equals the distance the weight moves upward. But, for a movable pulley, the distance you pull the rope upward is twice the distance the weight moves upward.

## The Block and Tackle

** A system of pulleys consisting of fixed and movable pulleys is called a block and tackle.**

**Figure 3** shows a block and tackle made up of two fixed pulleys and two movable pulleys.

If a 4-N weight is suspended from the movable pulley of the block and tackle in figure 3, each rope segment supports one-fourth of the weight, reducing the input force to 1 N.

**The IMA of a pulley system is equal to the number of rope segments that support the weight.** [IMA means Ideal Mechanical Advantage]

The **block and tackle** shown in **Figure 3** has an *IMA *of 4.

The *IMA *of a block and tackle can be increased by increasing the number of pulleys in the pulley system.