1. Changing the Direction of Pull:

* A single fixed pulley changes the direction of force by 180 degrees. If you pull down on the rope, the load will move up. This is useful when you need to lift something but can only apply force downwards, like when using a crane.

* A single movable pulley doesn't change the direction of force. You still pull in the same direction as the load moves, but the force required is halved.

2. Changing the Direction of Movement:

* A combination of fixed and movable pulleys can change the direction of movement. For example, a block and tackle system can lift a load vertically even if you are pulling horizontally.

In summary:

* Fixed Pulley: Changes the direction of the force by 180 degrees.

* Movable Pulley: Doesn't change the direction of force, but reduces the required force.

* Combined Systems: Can change both the direction of force and the direction of movement.

It's important to remember that pulleys don't change the amount of work required to move a load, just how much force you need to apply and in what direction.