We were discussing the projectile motion - trajectory equation, definition and formulas and we have also seen the concept of Terminal velocityapparent weight of a man in a lift and Lami's theorem in engineering mechanics with the help of our previous posts.

Today we will be interested here to start another important topic in engineering mechanics i.e. Definition of levers and it’s types or classifications with the help of this post.

### Levers

A lever is basically defined as machine member or a rigid bar which is hinged at one end or point. This hinge end or point will be termed as fulcrum. Lever will be free to rotate about this fulcrum.

A lever will have a point to apply the effort and it is termed as effort arm and similarly lever will also have a point for lifting the load which is termed as load arm.

Following figure, displayed here, indicates the lever. We can see here the fulcrum, load arm and effort arm. Load arm of a lever is also called as resistance arm.

Therefore, there will be three main components of a lever i.e. fulcrum, effort arm and load arm.

### Types of levers

There are basically two types of levers i.e. simple lever and compound lever as mentioned here.

### Simple lever

The lever which consists of one bar having one fulcrum will be termed as simple lever and it is displayed here in following figure.

We must note it here that this lever might be straight, curved or bent. Let us do some calculation for simple lever as mentioned below.
Where,
P is the effort applied on effort arm of length a
W is the load applied over the load arm of length b

Let us take moment about the fulcrum and we will have following equation as mentioned below

P x a = W x b

W/P = a/b

W/P will be termed as mechanical advantage and a/b will be termed as leverage of the lever.

After analyzing the equation of mechanical advantage, we can easily say that in order to increase the mechanical advantage, either we need to increase the length of a or we need to decrease the length of b.

### Types of simple levers

Further, simple levers are classified in following three types as mentioned below.
• First order simple lever or first class lever
• Second order simple lever or second class lever
• Third order simple lever or third class lever

### First order simple lever

If the fulcrum of lever is located in between the effort and load, then such lever will be termed as first order lever.

### Example of first order simple lever

Hand pump
Punching press hand wheel
Seesaw
Scissor
Rocker arm
Beam Balance

### Second order simple lever

If the length of effort arm is more than the length of load arm, then such lever will be termed as second order simple lever.

In second order simple lever or class 2 lever,

Length of effort arm > Length of load arm, hence applied effort will be less in case of second order simple lever.

### Third order simple lever

If the length of effort arm is less than the length of load arm, then such lever will be termed as third order simple lever. We can also say that in case of third order simple lever, length of load arm will be greater than the length of effort arm.

In third order simple lever or class 3 lever,

Length of load arm > Length of effort arm

Fig: First class, Second Class and Third class lever

### Example of third order simple lever

Tongs and treadle of sewing machine

### Compound lever

Compound lever is basically a combination of a number of simple levers. Following figure indicates the compound lever.

Mechanical advantage or leverage will be greater in case of compound lever as compared with simple lever.

Leverage of compound lever = Leverage of first lever + Leverage of the second lever + ……

Fig: Compound lever

### Example of compound lever

Platform weighing machine is the best example of a compound lever

Therefore, we have seen here the basics of levers and its types with the help of this post. We have also secured here the information of first order, second order and third order levers.

We have also seen here the various examples of simple lever, compound lever,  first order simple lever, second order simple lever and third order simple lever with the help of this post.

Further we will find out another concept in engineering mechanics with the help of our next post.

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We will find out now the in our next post.

### Reference:

Basic engineering mechanics and strength of materials, By M M Das , M D Saikia and B M Das