Recently, I made a catapult which uses a lever and we had to find the mechanical advantage of the lever. However, while I was looking through some other people’s catapults, I was constantly seeing MA which was less than one. From what I know, MA is the ratio of how much force the machine will output from the input force. So a MA of 4 would mean the machine would output a force 4x the input. If so, then what is the point of a MA less than one? Would it still be an advantage? If a mechanical advantage is less than one, that means that the input force would be higher than the output, so wouldn’t it be easier just to do it without the machine? So I did some research over the weekend. First let’s start off with levers. If the effort arm is closer to the fulcrum then the load, the mechanical advantage will be lower. This means that all 3rd class levers will have a MA <1 , 1st class levers could also have a MA <1. However, second class levers will not do this.
So then, what exactly is the point of a 3rd class lever? First let’s look a a 3rd class lever.
This baseball bat is a third class lever. As it turns out, the point of this third class lever baseball bat is not power, but speed or velocity. We exchange MA for speed, the baseball bat is one piece, meaning the side that you are holding when you swing, that side will move quicker than the other, so in order for the other side to move at the same speed and time, the velocity of that side must increase causing the bat to go at a faster speed. Which means when the bat hits the baseball, the baseball goes faster. So the point of the 3rd class lever is to make things go faster, or increase their velocity, right? Well, not exactly. That is the main reason for a 3rd class lever, but there are others too. For example, take a some tongs. Tongs are a third class lever. But the point of tongs isn’t to make something go faster, the point is to pick something up. Usually we use tongs for ice. What is the problem with ice? Ice is slippery and hard to pick up ( also no one wants your dirty hands touching the ice that will go in their drink) so we use tongs. MA doesn’t really matter here, because ice is so light, that we will only be losing such a small force, that it isn’t really noticeable. Tongs are also used to pick hot food up, because we don’t want to burn ourselves. Again, food is usually so light that the force lost isn’t noticeable. We don’t care about the small amount of energy being lost, we care about getting food. So 3rd class levers have all kinds of usages, and just because they have a mechanical advantage of less than 1 doesn’t mean they are completely useless.