Force and Motion
Concept: Levers and Their Uses
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.
|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.
|Wheelbarrow||Hole puncher||Bottle opener|
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 two/ 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|
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.
- 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.
Effort: It is a kind of force that is exerted by machines.
Fulcrum: It is the location on which the arm of the lever turns.
Rigid: An object is termed rigid when it is unable to bend or not flexible.
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.