The Effect of Lubricants on Mechanical Advantage

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Author: Alex, Grade 7


In this project I wanted to find out how lubricants affected the mechanical advantage of a pulley. To find this out I first gathered all of the needed material. Then I rigged a five-pulley system with a twelve-pound weight on the bottom. I used a spring scale to pull up the weight on the five-pulley system. I read the spring scale and recorded the ounces of weight required to lift a 12-lb. weight from the ground and recorded the number in my notebook. Then I took that number and divided it by the actual weight and got the mechanical advantage for the pulleys. Then I washed off the pulleys and added a lubricant to the axles and repeated the process.

The data shows a very small difference between each lubricant but that difference could mean the entire world if you were using a hundred pulley crane. It shows that lubricants increase the amount of mechanical advantage because they reduce friction. It also shows that the WD-40 is the best lubricant that I tested. It did the best job in reducing friction and it got the closest to the calculated mechanical advantage. By doing this it proved my hypothesis correct. It also decided the next lubricant I am going to use on my bike axle or my roller blades.

This project was a good success! It proved that WD-40 was the best lubricant that I tested and it came the closest to the calculated mechanical advantage. I chose this project because I have always been interested in pulleys and lubricants. When I started I didn't know that it would get this complex, but I rose to the challenge. It proved to be a good project and important too.


What lubricant has the most effect on the mechanical advantage of a pulley? Which one comes closest to the calculated mechanical advantage? Does friction have an effect on the mechanical advantage?


I predict that in my tests I will find that the actual mechanical advantage of the pulleys will not be the same as the calculated mechanical advantage because of the friction on the pulleys. I know that the calculated mechanical advantage will be eight but I predict it will be lower for the actual test. I also predict that the best lubricant will be WD-40 because it is the slipperiest. Also WD-40 will come the closest to the calculated mechanical advantage.


I learned about friction in my background reading. Friction is the heat and resistance caused when one object meets another object. Friction slows down movement. I also learned about lubricants. A lubricant is a friction reducer. The very best lubricant is the cartilage in the human body. It reduces friction 100%. How it does this is a total mystery because cartilage only works when the body is pumping blood. We have found other friction reducers. They're things that we use in our every day life, like WD-40, wax, motor oil, and soap.

In the reading I found out that a pulley has a wheel with rope or a belt passing through it. Pulleys are useful because they make pulling things easier or change the direction of the pulling. A pulley's advantage is called mechanical advantage. A pulley can be rigged in different ways, which will effect its mechanical advantage. If a pulley is hung vertically and it has more than one wheel it is called a block and tackle. If there is only one pulley and you are pulling down it is called a fixed pulley. A fixed pulley does not create mechanical advantage. It only changes the pulling direction. Another rig is a single pulley attached to the load. This pulley rig only has one pulley and you are pulling up.

Mechanical advantage is the sacrificing of distance for effort. The pulley is making you pull farther but dividing the force equally throughout the longer distance. You end up pulling further but less force is needed to pull. For example, if you have two pulleys and you lift a weight one-foot off the ground you will have to pull back two feet. Therefore you will use half the effort and the mechanical advantage is two.

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