Force and Motion

Concept: Levers and Their Uses

From this concept, the students will learn about types of lever and what are their uses. The students will get an idea about levers as simple machines.

After reading the concept, students will be able to:

• Explain what is a first class lever, what is a second class lever.
• Identify different parts of a lever like lever arms-the effort arm and load arm; the pivot point of a lever.
• Answer what is fulcrum.
• Know about pulley systems, what is a movable pulley with movable pulley examples, fixed pulley with fixed pulley examples.
• Understand the types of simple machines and examples of simple machines.
• Analyse the difference between pulley simple machine and lever simple machine.

Each concept is explained to class 4 students using descriptions, illustrations, and concept maps. After you go through a concept, assess your learning by solving the two printable worksheets given at the end of the page.

Download the worksheets and check your answers with the worksheet solutions for the concept of Types of lever and their Uses provided in PDF format.

What Is a Lever?

Levers are fundamental and simple machines. They are used to working with minimal effort. Every machine is an Examples of a lever.

Parts of a Lever:

• A lever has three parts—the fulcrum, the location where the effort is given, and the location where the load is put.
• The fulcrum is called the pivot point.
• In short, we can say that a lever is a rigid bar with a pivot point.

Classification of Levers:

Levers can be classified into—

• Class one/First-class levers.
• Class two/Second-class levers.
• Class three/Third-class levers.

1. Class one/First-class levers:

• First-class levers have a fulcrum (pivot) in the middle.
• The force is applied at one end, and the weight is located at the other end.

• The force is applied in one direction in first-class levers, and the load moves in the opposite direction.
• The length of the effort arm where the force is applied can be greater, equal, or less than the length of the load arm.

Examples:

Pliers	Scissors	Crowbar
Seesaw	Wheel and axle	Weighing balance
Claw and hammer	Spoon	Tubewell

How Does a First-Class Lever Work?

• Have you ever tried to open the lid of a can with a screwdriver?
• When you do that, you have to put effort on the screwdriver's handle at a greater distance than on the load.
• In this case, the rim of the can be considered the fulcrum situated between the effort and the load.
• Here, the lid is the load that is nearer to the fulcrum.
• Since the effort arm is greater than the load arm, we can generate a large force on the load and open the lid.

2. Class Two/Second-Class Levers:

• Second class levers have a pivot point (fulcrum) at one side, and effort is put on the other side.
• The force is applied at one end of the lever, and the weight is located in the middle.
• In these levers, the load is positioned in the middle.
• These levers can magnify the effort force because the force is applied at the opposite end of the lever from the fulcrum.
• In class two levers, the movement of the force and the load are in the same direction.
• The length of the effort arm is always greater than the length of the load arm.

Examples:

Wheelbarrow	Hole puncher	Bottle opener
Nutcracker	Nail clipper	Oar

How Does a Second-Class Lever Work?

A classic example of a second-class lever is a wheelbarrow.
Wheelbarrows are used to lift heavy loads and cross a large distance carrying that load.
In the case of a wheelbarrow, the fulcrum is located on the axle and the wheel.
The effort can move a large distance to lift a heavy load.

Another example of a second-class lever is bottle openers.
The effort arm of the bottle opener is greater than the load arm.
Both the effort and the load work in the same direction.
The pivot point or fulcrum is located at the end, which opens the bottle cap.
With minimal effort, maximum force can be created with the effort arm as it is the largest arm to open the corks and the bottlecaps.

3. Class Three/ Third-Class Levers:

• In third-class levers, the effort is located between the load and the fulcrum (pivot).
• In these levers, the distance moved by the load is always greater than the distance moved by the effort.
• To make these levers work, one must apply a massive force to the load.
• All kinds of third-class levers have a mechanical disadvantage.
• In the case of third-class levers, the input force or the effort is greater than the force produced on the load.

• In a third-class lever, the load and the effort always move in the same direction.
• In all class three levers, the length of the load arm is always greater than the length of the effort arm.

Fishing rod	Broom	Bow and arrow
Baseball bat	Tweezers	Spade

How Does a Third-Class Lever Work?

• The human arm is an example of a third-class lever.
• When we lift anything using the forearm, we use a class three lever.
• In the case of a human arm, the elbow is considered the fulcrum.
• The load is on the hand, and the effort is located between the elbow and the load.

Pulleys:

• A pulley is a simple machine. It is used to lift heavy objects.
• A pulley consists of a wheel that has a grooved track for the rope, chain, or belt to move through it.
• When a force is applied at one side of the rope or the belt or the chain, it uses the pulley system and moves in a different direction.
• Pulleys can be of two types—
•  Fixed pulleys
•  Movable pulleys

1. Fixed Pulleys:

• The pulley remains attached to a fixed position with a rope on it in the fixed pulley system.
• These pulleys rotate on their axis at a fixed place.
• The fixed pulleys change the direction of effort.

Examples: Flag poles, sail masts, etc.

2. Movable Pulleys:

• These pulleys do not remain attached to a rigid support.
• These pulleys are free to move up and down.
• Movable pulleys remain attached to other objects with the same rope.

Examples: Construction cranes, elevators, etc.

New Words:

Did You Know?

• Wheel and axle are present in bicycles, sewing machines, coffee beaters, doorknobs, etc.
There are many more simple machines except pulleys and levers.
Examples: An inclined plane is used to lift heavy objects with less force. A screw is also a simple machine that helps to hold things together. A wedge is a simple machine that is used for cutting.