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A Lever is a simple machine that usually consists of a rigid bar or rod that rotates about a fixed pivot point called the fulcrum. If you apply a force to a lever it will rotate about the fulcrum. Common examples of levers are seesaws, wheelbarrows, crowbars and nutcrackers. The advantage of using a lever is that with a small amount of effort, you can move a very big load.
For example with a crowbar, a relatively small effort is applied at the end farthest from the fulcrum to lift a heavy weight that is close to the fulcrum. Many other common tools and instruments utilise the principle of the lever.
A lever has two related forces associated with it called load and effort. In the third century BC, the Greek mathematician Archimedes first described the principle of the lever that can be expressed as:
x its distance
from the fulcrum
|=||The load |
x its distance
from the fulcrum
TYPES OF LEVER
A first class lever is one where the fulcrum is between the effort and the load just like a seesaw or crowbar (E F L or L F E).
In the second class lever, such as a wheelbarrow, the load is placed between the effort and the fulcrum (F L E or E L F).
In the third class lever, such as a fishing rod, the effort is placed between the load and the fulcrum (F E L or L E F).
So how do you remember which is a 1st, 2nd or 3rd order lever? When I was studying mechanics at college I was faced with the same problem so I wrote out the initials for load, effort and fulcrum as follows:
|1st Order||2nd Order||3rd Order|
|E F L||F L E||F E L|
So to remember the different classes I imagined a flea called Ethel having a fall so: ETHEL (E F L) the FLEA (F L E) FELL (F E L).
Now every time that I think about levers and which type is what class, I just recite "Ethel the flea fell". I then think "Ethel = E F L, so a first order lever (Ethel is the first word of the mnemonic) has the fulcrum between the effort and the load" and so on. I know it sounds crazy and perhaps a little silly, but I did that over 15 years ago and I can still remember it. That is how powerful this seemingly innocent play on words and imagery can be.
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