Pulley

 

A pulley is a grooved wheel that turns on an axle. The groove in the wheel causes the rope or cable to ride on the wheel without slipping off.

 

 

 

 

 

The pulley is generally used to assist lifting heavy weights.

1.  The pulley can change the direction of a pull.  In this case, pulling down on the rope will lift the weight up.  With just one pulley as shown below there is no saving of effort, but it provides a way to maneuver the weight more conveniently.

2.  With the pulley arrangement shown below, less effort is required.  Half the weight is supported by the overhead beam, and half is supported by the person holding the other end of the rope.  The weight is shared so the human effort is less.  However, now the rope will have to be pulled twice the distance.  You would have to use half as much force to lift the weight, but you would have to pull the rope twice as far, as compared to the first example shown above.

In the pulley simulation program, let's take the 1 to 1 and 2 to 1 pulleys for comparison.  You will feel twice as much effort when pulling the 1 to 1 pulley than the 2 to 1 pulley.  For the same amount of rope you pull in the 2 to 1 pulley case, the weight only reaches half the height of the 1 to 1 pulley (as shown below).  The third choice is the 4 to 1 pulley, which behaves in a similar way, but the pulling effort is one-fourth of the 1 to 1 pulley effort, and the lifted height for the same rope length will be only one-fourth of the 1 to 1 pulley lifted height.