# Pulley Physics (Tension / Effort / Load Force and Motion Explained)

After working on my lever and bicycle gearing physics video I got to thinking about pulleys.

What is a pulley? 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
Lets take a look at a one pulley system. If we have one pulley it changes the direction of the effort from going down to pulling the load up. There is no mechanical advantage multiplier for a single pulley system.

Now lets take a look at a two pulley system. If we zoom in to the section that is past the first pulley we see that the 2 tension forces cancel out the load weight. The weight of the crate is distriputed between the two ropes equally. Being that the tension is equal along the whole length of rope or cable the effort force required to lift the crate is cut in half. So half the load weight equals the effort force. This pulley system has a mechanical advantage of 2.
Now you are probably thinking what is the cost. The cost is that in the single pulley system if you pull one meter of rope the load lifts one meter.

In the 2 pulley system if you pull one meter of rope the load only moves by half a meter. 2 half meters are taken up on each side of the green pulley to account for the one meter of pull. So similar to levers we increase the displacement by 2 and cut the force needed to move the object in half

That conclude this video thanks you for watching hopefully I earned a like or subscription