Different Types of Levers
This is a basic physics GCSE tutorial taking a brief look at different classes of levers, with very real and practical examples.
Different types of levers
There are three different types of levers - aptly referred to as first, second and third class levers. The first and second class levers work as force multipliers; they allow you to do a large amount of work with little effort. You can refer to this as a mechanical advantage.
The third class levers offer a distinctly different set of advantages, which are discussed in detail below (under third class levers).
A double is one that is made from two levers attached to each other at the fulcrum. The two levers work together to do the one job. They can be made of any two of the same levers : i.e. two 1st, 2nd, or 3rd class levers.
First Class Levers
A first class lever has its pivot or fulcrum at some point in the middle, although not necessarily in the exact centre. A very common example is the seesaw. If the load and the effort are equidistance (equal distance) from the fulcrum, the load force and effort force will be the same. The further away the effort is from the fulcrum in comparison to the load, the less effort is needed to lift the same load.
Double Class 1 Lever
A pair of scissors / garden pliers is an example of a double class 1 lever. As discussed above, the greater the distance between the fulcrum and the effort force (and/or the closer the load is to the fulcrum) the less effort is needed to do the same work. You'll intuitively know this is the case because things are always easier to cut when you have them wedged in nice and close to the fulcrum of a pair of scissors or pliers, compared to the very edge of the blades.
Second Class Levers
A second class lever has the load in the middle, with the fulcrum and the effort applied on either end. A classic example is the wheelbarrow.
When in use, the handlebars move a much greater vertical distance than the load. This reduces the effort force required to lift the load.
Third Class Levers
A third class lever has its effort in the middle, with the load and fulcrum located on either side.
Unlike the first or second class levers, there is larger movement in the loaded end than where the effort force is applied (in the middle). This means that this type of lever is not used to generate large forces, but rather to exert large velocities.
A baseball bat is a good example of a third class lever. In this case, the very end of the bat acts as a fulcrum. You apply the effort at the handle bar, and the load is at the other end of the bat (the end that strikes the ball).
Third class levers require more input effort than the output effort, which is not typically what you'd associate with a lever. The advantage though is that the loaded end will move a greater distance (and hence with greater speed) than the input effort end. This means the ball will launch off at a faster speed, which is really useful for a game like baseball.
Double Class 3 Levers
You can combine two third class levers to give you tools that are useful for helping you hold something without damaging it. A great example of this is a pair of tweezers (mouse over to see the two third-class levers below). This is because the force you apply is smaller than what is exerted on the object (e.g. a flower petal). The other benefit of a tweezer is it allows you to grip something very small i.e. it gives you good precision. This is necessary when you are dealing with small objects like eye-brow hairs or splinters.