How Does a Pulley System Work in Physics?
You might have seen fictional characters who pull trucks with their hair and pull trains with their teeth. But you may not know that science can make you so strong. If you want to lift heavy weights, use the knowledge of science and do amazing things using a device called a pulley.
A pulley is a collection of wheels looped over a rope that is used to lift things.
A pulley system is an easy way to lift heavy objects, as compared to lifting the object barehanded. A single pulley only serves to change the direction of the applied force. When two or more forces are used in a system, then the pulley not only changes the direction of applied for but also multiplies the input force. If one fixed and one movable pulley is applied in a system, the system almost doubles the amount of force applied by a person.
Every now and then you may have encountered super-strong fictional characters who can literally do almost anything, such as pulling the trains or other such heavy vehicles all by themselves, etc. But what if someone tells you that you can be just as strong as one of your favorite characters. Well, you might be perplexed by now, but here is the interesting thing, though of course as human beings, we cannot be that super strong all by ourselves, but science can kind of make us that strong. For example, science enables us to lift heavy weights and other such things, and science does it by using a device called “Pulley”.
The Pulley system is an important part of our modern-day life because so many things have become easy for us because of the pulley system. And as a student of science, it is necessary for you to learn about the science behind the pulley system, that is to say, how the pulley system works. And to do so, you require an explanation of the pulley system in which you can understand everything, and which clears all the questions that you may have regarding the concept of the pulley system because otherwise, you are only going to be confused.
Hence to make things easy for the students Vedantu provides a Complete Explanation of the Pulley System, along with its Definition and Mechanism. And this explanation that Vedantu provides is very easy to understand. After reading it thoroughly you are not going to have any problem in understanding this wonderful mechanism called “Pulley System”. And also, Vedantu provides this explanation of the Explanation of Pulley System, along with its Definition and Mechanism completely free of cost.
Pulley System in Physics
A wheel on a shaft or an axle is designed for supportive movement. It changes the direction of the belt or the cable and also transfers power between the shaft and the belt or cable.
A pulley system that has a support frame or shell doesn't transfer power to the shaft. It is used to exert force and guide the cable in a specific direction. The shell, which is used as a support in the pulley system, basically acts as a block. It is referred to as a sheave.
The circumference of the pulley system is surrounded by flanges that contain grooves or grooves to locate the table and the belt. This system of a pulley is driven by a rope, cable, belt, or chain.
The pulley system is assembled in a way to ease the mechanical effort required to lift heavyweights.
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It is also assembled in a way such that the chain or belt will have high efficiency for transmitting power from one shaft to the other.
An Overview of the Pulley System
Pulley is nothing but a wheel built on an axle, a central shaft which is made for the rotating wheel or a gear, and it is designed to assist the movement of a cable or a belt, and it serves the purpose of transferring the power between the axle or the shaft, and the cable or the belt. Mostly Pulley has grooves, that is to say, a rather long and narrow indentation built in a given material that allows the other material to move. These grooves are built between the flanges, covering the circumference of the material, and then there is a rope, or the belt, or the chain which serves the purpose of the drive mechanism.
A Brief History of the Pulley System
The Pulley system is one of the oldest mechanisms that we are using, for instance, the evidence of the development of the pulley system can be found in many ancient civilizations, such in ancient Egypt, the use of pulley system can be found around in their twelfth dynasty, which dates back to 1991 and 1802 BCE. Even earlier than that the evidence of the Pulley System can also be found in the Mesopotamian civilization in the second millennium BCE. Also, in Egypt during the period of Roman rule, the Pulley system was used as a simple machine to lift heavyweights.
From this brief discussion, you can understand how old the pulley system is, and how important it is for us as well.
Also, if you wish to learn more about the pulley, then you may like to follow this link: Pulley - Definition, Description, Types, Formula, and Applications (vedantu.com)
Different Types of Pulley System
There are various types of Pulley mechanisms, some of them are explained below in a brief manner:
Fixed Pulley: As the name suggests, this particular pulley mechanism has a wheel that cannot be moved or rotated in any direction, that is to say, it is a fixed wheel.
Movable Pulley: Again, as the name implies, when the wheel of the pulley can move and rotate freely then it is considered as a movable pulley.
Compound Pulley: When the pulley system combines the mechanism of both the system previously described, that is to say, Fixed and Movable pulley then it is the compound pulley.
Pulley Mechanism
A pulley has a unique mechanism, which makes it easier to lift heavy loads with less effort; for this reason, it has become one of the most important tools in the engineering industry. It has a wide range of applications in different industrial machines.
The work of a simple pulley is to lift a heavy load with ease by using a rope and a wheel. However, there are some other types of pulleys that have a very complex mechanism.
The working mechanism of different types of pulley systems is given here below:
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a. Fixed Pulley
The simplest type of pulley system contains a wheel that is not free to move and rotate in any direction; this is a fixed wheel. The amount of force applied to the pulley system is the same as the weight of the pulley. This pulley system requires very little space to operate and has the simplest mechanism among all pulley systems.
b. Movable Pulley
This is also a simple pulley, but the wheel of this pulley can both move and rotate. In this pulley system, less force is required as compared to the weight of the object, to lift the object. The wheel of this pulley system translates the motion of the pulley system. This pulley system is used in almost all kinds of pulley systems and hence is very common.
c. Compound Pulley
The combination of a simple pulley and a movable pulley is called a compound pulley. It is also called a combination of the pulley. It is oriented in such a way so as to reduce the effort to less than half of the weight of the load. Thus the pulley system is mainly used by cranes to lift heavy objects of steel and concrete in construction sites.
d. Block and Tackle Pulley
The block and tackle or just tackle is a pulley system that consists of two or more pulleys attached with a rope or cable and is used to lift heavy-weight loads. In this pulley system, the pulleys are assembled in the form of blocks. The blocks are then paired in which one pulley is fixed, and the other pulley moves.
Rope Pulley System
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Pulley in oil derrick
The above-mentioned figure is a hoist using a compound pulley system that has a yielding capacity of 4. The hoist consists of one single fixed pulley and two movable pulleys (which are joined with each other) attached to the hook. One of the ends of the chain of the pulley is attached to the pulley while the other is attached to the winch.
A rope and a pulley system contain a single rope that is used to transmit force from one pulley to another, either to move or lift a load. The rope used can be a light rope or a chain that can also be used. The Renaissance scientists have included this system of the pulley in the list of simple machines.
FAQs on Pulley System Explained: Concepts & Uses
1. What is a pulley system in Physics?
A pulley system is a simple machine consisting of a wheel on an axle or shaft, designed to support movement and change the direction of a taut cable or rope. In physics, it is used to lift heavy loads by applying a smaller force. The core components are the pulley (wheel), axle, and the rope or belt that runs over the pulley.
2. What is the working principle behind a pulley system?
The working principle of a pulley system is based on distributing a load's force across multiple sections of a rope. When you add more pulleys (creating a compound system), the load's weight is shared among several rope segments. This significantly reduces the amount of effort required to lift the object, a concept known as providing a mechanical advantage. The trade-off is that you must pull a longer length of rope to lift the load to the same height.
3. What are the main types of pulley systems?
The primary types of pulley systems are categorised by their arrangement and function:
Fixed Pulley: The axle is fixed in one place. This type changes the direction of the force but does not reduce the effort required (Mechanical Advantage = 1).
Movable Pulley: The axle is free to move. This type reduces the effort required to lift a load (Mechanical Advantage = 2) but does not change the force's direction.
Compound Pulley: A combination of fixed and movable pulleys, like a block and tackle. This system is designed to provide a significant mechanical advantage, making it easy to lift very heavy objects.
4. What are some common real-world examples of a pulley system in action?
Pulley systems are found in many everyday machines and tools. Some common examples include:
Elevators (Lifts): Use multiple pulleys and counterweights to move the car up and down.
Cranes: Employ complex pulley systems to lift extremely heavy materials at construction sites.
Flagpoles: Use a simple fixed pulley to raise and lower a flag.
Gym Equipment: Weight machines often use pulleys to redirect force and allow for various exercises.
Wells: A traditional well uses a pulley to make it easier to draw a bucket of water from the ground.
5. How does a single fixed pulley differ from a single movable pulley?
The key difference lies in their function and mechanical advantage. A single fixed pulley has its axle anchored and only changes the direction of the applied force, offering no reduction in effort (Mechanical Advantage is 1). In contrast, a single movable pulley has its axle attached to the load and moves with it. It halves the effort needed to lift the load (Mechanical Advantage is 2) because the load is supported by two rope segments.
6. How exactly does a pulley system provide a mechanical advantage?
A pulley system provides a mechanical advantage by distributing the weight of the load among multiple strands of the rope. When a load is hung from a system with movable pulleys, each rope segment supporting the load shares a fraction of the total weight. For an ideal system, the mechanical advantage (MA) is equal to the number of rope segments directly supporting the load. For example, if a load is supported by 4 rope segments, the effort required is only one-fourth of the load's weight (MA = 4).
7. How do you apply Newton's second law to solve problems for a simple Atwood machine?
To solve problems for an Atwood machine (two masses connected by a string over a single pulley), you apply Newton's second law (F=ma) systematically:
First, draw a Free Body Diagram (FBD) for each mass, showing the downward force of gravity (mg) and the upward force of tension (T).
Define a positive direction of motion (e.g., clockwise).
Write the net force equation for each mass. For the heavier mass (m1), the equation is m1g - T = m1a. For the lighter mass (m2), it is T - m2g = m2a.
Solve these two simultaneous equations to find the system's acceleration (a) and the tension (T) in the string.
8. What is the significance of tension in a pulley system's rope?
Tension is the pulling force transmitted axially by a rope or string. In a pulley system, its role is critical: it's the force that connects and acts upon all masses and pulleys. In an ideal, massless string, tension is assumed to be uniform throughout its length. It acts upwards on the suspended masses, counteracting gravity, and is the internal force that allows the effort applied at one end of the rope to be transferred to lift the load at the other end.
9. How do the mass and friction of a real pulley affect its efficiency?
In real-world scenarios, ideal conditions do not exist. The mass and friction of a pulley reduce its efficiency:
Mass of the Pulley: A pulley with mass has rotational inertia. Part of the applied effort must be used to provide the torque needed to make the pulley rotate. This means less force is available to accelerate the load, effectively increasing the effort needed.
Friction: Friction at the axle opposes the pulley's rotation. This dissipative force converts some of the input work into heat, meaning the output work (lifting the load) is always less than the input work. This lowers the overall efficiency of the system.
10. Can a single fixed pulley ever reduce the force needed to lift a load? Explain the physics.
No, a single fixed pulley cannot reduce the magnitude of the force needed. According to the principles of mechanics, its mechanical advantage is 1 (ideally). This means the effort force you apply must be equal to the load force. The true benefit of a single fixed pulley is the change in the direction of force. It allows you to pull downwards to lift a weight upwards, which is often more convenient and allows you to use your body weight to assist.
