[Physics Class Notes] on Types of Lever Pdf for Exam

In our daily life, we see many objects around us such as a see-saw in the park, spoons in the kitchen, scissors, bottle openers, joints in the human body.

 

What is Lever?

The lever is a rigid bar that allows a heavier or a steadfast object to lie on the fixed point with a smaller force.

Three different types of levers exist, depending on where the input force, fulcrum, and load are. 

On this page, we shall learn the following things: 

• What are simple machines?

• Fulcrum, Lever, Effort, Load

• First-class, second-class and third-class lever

• Mechanical advantage (MA)

• Examples (Real-life)

 

What are Simple Machines?

The word machine has come from the Greek word which means “to help make things easier.”Energy remains conserved because machines can’t do more work than the energy we put in. The lever is nothing, but a rod and 

The thing we encounter in day-to-day life having a rod-like function is “Lever.” Lever has a fixed point through which it is easy to rotate it about that point. Such as a bottle opener, scissors, pliers, stapler, nut-Cracker; etc.

 

Let’s Talk About Basic Definitions:

1. Load (L): A resistive force that is to be overcome by a machine is called the Load.  S.I. The unit is Newton (N).

2. Effort (E): An external force applied to a simple machine to overcome a load is called Effort. S.I. The unit is Newton (N).       

3. Fulcrum (Pivot, F): The point on which something turns or is supported.

4. Mechanical advantage (MA): The ratio of Load (L) to overcome the magnitude of Effort (E).               

Where MA is nothing but the ratio of the Effort arm to the Load arm, which we would be discussing in the class of Levers.

MA  = Effort Arm (E)  /  Load Arm (L) 

Effort Arm (E) = The distance between the effort (force) and the Fulcrum (pivot)

 Load Arm (L) =  The distance between the Load and the Fulcrum (pivot)

 

Types of Levers

First-Class Lever

Here, it is a first-class lever.

In this, we can see that we have to apply an effort (force) against gravity. 

Like, in a garage, a screw jack is fixed at the bottom and as we start rotating the jack, the car moves upwards, here we applied little force, and the car applied that force to move upward.

Second-Class Lever

Did you notice that when you try to tear the paper into equal parts manually, it takes much time?

If you use scissors, then the time would be saved, though the effort applied was less, the work got done in speed.

Which means the speed is increased here to get the job done earlier.

Third-Class Lever

You might’ve been to villages, where people 

depending upon the well as a water resource, they apply their effort upward in pulling out the water from the well via the bucket attached to the string, but it is easy to use a pulley, then the effort would’ve been downwards (towards the gravity). Hence the effort applied would be less.

 

Classification of Levers based on MA

 

It can work as a force multiplier, speed multiplier and in changing  the direction of Effort As well (Depending on the value of MA)

Let’s Understand:

This is a first-class lever, it has Fulcrum (pivot) in the middle, Load at one end, and effort on the other.

1. See – Saw

Here,  in this case:   

The Fulcrum (pivot) is between the Load and the Effort such that

Length of Load Arm (La) = Length of Effort Arm (Ea).]

 MA (Mechanical advantage) = Ea / La

As  Ea = La          

MA = 1

Which means the change in direction.

2. Pliers                          

Here, Ea >  La, as you can see in the image above that the Effort Arm is greater than the Load Arm.

 As we know, MA = Ea/ La,

 Here, Ea > La, MA > 1

Therefore, it works as a Force Multiplier.

3. Scissors   

In the above image of scissors, we can see that the Length Arm > Effort Arm:

As, MA = Ea / La

And, Ea < La

So, MA  < 1

Here, it works as a Speed Multiplier

In the above image, La > Ea.

So, MA < 1, therefore works as a

Speed Multiplier.     

Here, La >  Ea

MA = Ea / La

As, Ea < La, implies that MA < 1

 

Change in Direction

 Velocity ratio:= Distance traveled by effort (m) / Distance traveled by Load (m)                     

  Work Input:= Effort (E) * distance traveled by an Effort (n)

 Efficiency (p):= Work output / work Input

=  Mechanical advantage / Velocity ratio 

 =  M.A. / V.R.

 

Summary: 

We call levers simple machines because they have only two parts – Fulcrum and the Handle, where the handle or bar of the lever is called the “Arm,” and Fulcrum is the point on which the lever rotates.

 

Short Question answers:

Q1: The efficiency of a machine is 60 %. If 500 Joule of energy is given to the machine. What is its output?

Sol
: Efficiency (p) = 60%, Input (i) = 500 J

Output = p * i

 = 60/100 * 500

Therefore, Output  = 300 J

Q2: Explain why scissors for cutting cloth may have blades longer than the handles but shears for cutting metals have short blades and long handles?

Ans:  A pair of scissors used to cut a piece of cloth has blades longer than the handles so that the blades move longer on the cloth than the movement at the handles. While shears used for cutting metals have short blades and long handles because it enables us to overcome 

large resistive force by a small effort.

Q3: A pair of scissors has its blades 10 cm long, while its handles are 2.5 cm long. What is its mechanical advantage? 

Ans: Effort Arm ( Ea) = 2.5 cm

Length Arm = 20 cm

M.A. = Ea/ La 

= 2.5/ 10

Therefore, M.A.    =   0.25

Lever and its Type

The lever can be defined as a machine that is quite simple in its arrangement and is composed of a rigid rod or a beam that is put on a fixed hinge which is called the fulcrum. This, the fulcrum is the point where the lever is placed and this either turns or supports it. This is then used to transfer a force to a load which is advantageous mechanically. The lever is a structure that can rotate in itself at a point. There are 3 types of this structure, namely that-class lever, second class and third-class lever. They are classified according to the fulcrum, the force and the load.

The main use of levers is mechanical advantage which is defined as the quantity a special machine multiplies a force applied. This can be calculated or found out by considering the location of load, effect and fulcrum which in turn gives the type of lever and the amount of mechanical advantage the machine has. When the effort is in a longer distance from the fulcrum then the load becomes easier to move. It is equal to the ratio of the effort of the load and the distance from the effort of fulcrum to the load of the fulcrum’s distance. If the distance of effort to the fulcrum is larger than the load of the fulcrum’s distance then there is a mechanical advantage in the lever. Thus, the ratio of the two distances will be greater than one which means that when there is a long distance from fulcrum to the effort and a short distance from the fulcrum to the load then a small effort will move a heavy or large load.