Three pulleys are used in this system to reduce the amount of force needed to lift a mass. By distributing the weight of the mass among the three pulleys, the force required to lift the mass is divided by three, making it easier to lift.
The mechanical advantage of using three pulleys in this system is 3. This means that the force needed to lift the mass is one-third of the actual weight of the mass. So, if the mass weighs 300 N, only 100 N of force is needed to lift it.
When using three pulleys, the direction of the force needed to lift the mass changes. Instead of pulling straight up on the mass, the force is applied horizontally to the rope. This horizontal force is then distributed among the three pulleys to lift the mass.
Using a pulley system to lift heavy objects has several advantages, including reducing the amount of force needed to lift the object, making it easier for a single person to lift heavy loads, and allowing for more precise control over the lifting process.
While pulley systems are very effective at reducing the amount of force needed to lift heavy objects, they do have limitations. For example, friction in the pulley system can reduce the overall efficiency of the system, and the weight of the pulleys themselves can add to the total weight that needs to be lifted.