Pulley

Nathan, Blanca

What it is

a pulley is a wheel with a grooved rim around which a cord passes. It acts to change the direction of a force applied to the cord and is chiefly used (typically in combination) to raise heavy weights.

How it provides mechanical advantage

It changes the direction of the force. This can be an advantage in cases where you would have to pull something upwards, using only your muscles, because by changing the direction you can use your weight too. You do the same amount of work, but less force has to be applied over a greater distance.

Examples

Practice problem

Mechanical advantage = Out Put Force / In Put Force

1) Laura wants to lift up the 150N mainsail of a sailing boat. To do this, she uses a pulley to connect one end of the rope connecting with the mainsail to the other end of the rope and pulls down on it to lift the mainsail. If Laura weights 250N, what is the mechanical advantage of using a pulley to lift up the mainsail?

Answer

mechanical advantage= 250/150 = 1.67N