The ability to do work is called energy, and work is moving something against a force, like gravity.
Energy is a property of matter that can be converted into work, heat, or radiation. In simple words, energy is the capacity for doing work. When we do work on an object, some of our energy is transferred to that object. When energy is transferred, the object upon which the work is done gains energy. Science has classified energy into two main forms: kinetic energy and potential energy.
The SI unit of energy is the joule (J). or 1 kJ = 1000 J.
There are many different forms of energy, including:
Table of Contents
Why Energy is called the Ability to do Work?
- Energy is often referred to as the ability to do work.
- Energy is required to accomplish a physical or mechanical task.
- When work is done, energy is transferred from one form to another or from one object to another.
- For example, when a force is applied to an object, energy is transferred to the object, and work is done on it.
- The amount of work done is equal to the amount of energy transferred.
- Therefore, energy and work are closely related and can be thought of as two sides of the same coin.
Simple Daily Life Examples of Energy
- Turning on the light: When you flip a switch to turn on a light, you’re using energy to make the light bulb glow.
- Cooking food: When you use a stove or microwave to cook food, you’re using energy to heat it up.
- Riding a bike: When you pedal a bike, you’re using energy from your muscles to move it forward.
- Listening to music: When you turn on your music player, it uses energy to play the songs.
- Playing a video game: When you play a video game, your device uses energy to run the game and display it on the screen.
- Drinking a cold beverage: When you drink a cold soda, you’re feeling the energy transfer from the cold drink to your body.
- Watching TV: When you watch TV, you’re using energy to power the TV and the cable or satellite box.
What is work?
Work is defined as the force exerted multiplied by the distance over which it is exerted. In equation form, work (joules) = force (newtons) x distance (meters), where a joule is a unit of work. One of the simplest examples of work is lifting a weight from the ground and putting it on a shelf.
The Unit of work is the joule. One joule is the amount of work done when a force of 1 Newton is applied over a distance of 1 meter.
Joule = N.M
Joule= kg.m2/sec2
Examples of Work
- The work (W) done in lifting a brick of mass 2 kg to a height of 5m above ground will be 100J.
- If a man pulls a cart through 35 m with a force of 300 N. The W will be 10500 J.
- When a person takes a bucket to some distance, his work done is zero because force and displacement are perpendicular.
- If we lift a load from the earth to some height, the work is done.
Relation Between Energy and Work
| Concept | Explanation |
|---|---|
| Energy | A fundamental quantity that can be defined as the capacity to perform physical or mechanical tasks. |
| Work | The transfer of energy that occurs when a force is applied to an object and it is displaced through a distance. |
| Relationship | Energy and work are closely related and can be thought of as two sides of the same coin. When work is done, energy is transferred from one form to another or from one object to another. The amount of work done is equal to the amount of energy transferred. |
| Mathematical Relation | Work (W) = Force (F) x Distance (d); Energy (E) = Work (W); so E = F x d. This equation shows that the amount of energy transferred is directly proportional to the amount of work done, which in turn depends on the force applied and the distance through which the force acts. |
| Daily Life Examples | Examples of work being done that require energy include lifting a heavy object, pushing a car, running, cycling, or even just moving your arms to type on a keyboard. In each case, energy is transferred from the body or external source to perform the work. Energy is also required for many everyday tasks, such as heating or cooling a home, cooking food, or powering electronic devices. |
Energy-Key Points
| Definition of Energy | Energy is the ability to do work. For instance, In hydro power plants, water drives the turbine blades, which turn a generator, which finally delivers electrical energy. |
| Unit of energy | The standard unit is the joule (J). One joule is the energy equivalent of one newton of force acting over one meter of displacement. |
| Forms of Energy | Examples of energy include electrical, nuclear, and chemical energy. |
| Daily life examples of energy | Heating and cooling of our homes. Driving cars. Manufacturing the products. |
Work-Energy Theorem
The Work-energy theorem states that the work done by the sum of all forces acting on an object equals the change in kinetic energy of the object (or) the net work done on a system equals the change in kinetic energy. Check the derivation of the work-energy theorem.
Work done = K.Ef-K.Ei (Network done = change in Kinetic Energy)
Kinetic Energy and Potential Energy
Kinetic energy is the energy that a moving object has due to its motion. The faster an object moves, the more kinetic energy it has. The kinetic energy formula of a moving object equals one-half the product of its mass and the square of its velocity.
Potential energy is the energy that an object has due to its position. If the object is lifted straight up at a steady speed, then the force (F) required to lift it to the height (h) is equal to its weight (mg).
In other words, when an object is lifted to a higher elevation, work is done on it and the energy transferred is stored; the quantity of energy stored is mgh. This stored energy is gravitational potential energy with the relationship of w = mg.
Summary
- The ability to work is called energy. Energy is a material attribute that can be turned into work, heat, or radiation.
- The Work-energy theorem states that the work done by the sum of all forces acting on an object equals the change in kinetic energy of the object.
- Work is a scalar quantity and its unit is the joule.
- One joule is one unit of work. Work is one joule if a force of 1 Newton is applied across a distance of 1 meter.
- The kinetic energy of a body is equal to one-half the product of its mass, m, and the square of its velocity.
Related Topics
Power Units- The Basics
Relativistic Kinetic Energy
Can Velocity be Negative?| Examples
Can Work Be Negative?
Multiple Choice Questions
- Which of the following best describes energy?
A. The ability to perform physical or mechanical tasks
B. The amount of force applied to an object
C. The distance an object moves when a force is applied to it
D. The speed at which an object moves when a force is applied to it
Answer: A. The ability to perform physical or mechanical tasks - What is work in terms of energy?
A. The capacity to do physical or mechanical tasks
B. The transfer of energy that occurs when a force is applied to an object and it is displaced through a distance
C. The amount of force applied to an object
D. The distance an object moves when a force is applied to it
Answer: B. The transfer of energy that occurs when a force is applied to an object and it is displaced through a distance - Which of the following equations represents the mathematical relationship between energy and work?
A. E = F x d
B. W = F x d
C. F = m x a
D. E = m x c^2
Answer: A. E = F x d - What is an example of work being done that requires energy?
A. Watching TV
B. Sleeping
C. Running a marathon
D. Sitting in a chair
Answer: C. Running a marathon - What is the relationship between energy and work?
A. They are unrelated concepts
B. Energy is the cause of work
C. Work is the cause of energy
D. Energy and work are closely related and can be thought of as two sides of the same coin
Answer: D. Energy and work are closely related and can be thought of as two sides of the same coin
Frequently Asked Questions
Some of the frequently asked questions are given below
1. Can force be negative?
To answer the question “can force be negative”, we need to understand the concept of positive direction and negative direction.
- Force is negative. If the applied force is in the opposite direction to the displacement of the moving object.
- Forces that are aimed at the right are usually called positive forces.
- Forces that are aimed to the left are usually said to be in a negative direction.
2. What is instantaneous velocity?
The velocity of an object at any single instant or point is called instantaneous velocity.
It is similar to average velocity, except the time interval is infinitely small.
The formula for instantaneous velocity is the limit as the time approaches zero of the change in displacement over the change in time.
3. Momentum equation?
The momentum equation is simply the product of the mass and velocity of a moving object.
If an object is moving and has mass, then it has momentum.
The momentum of a body refers to the quantity of motion a body possesses due to its mass and velocity.
4. Can displacement be negative?
Displacement can be negative since it is a vector variable that depends on magnitude and direction. The negative sign just indicates the direction. Check the full article here“can displacement be negative?”.
5. What is the ability to do work called?
In physics, the ability to do work is energy. It can take many forms, including potential, kinetic, thermal, electrical, chemical, radioactive, and others. Furthermore, there is heat and work—that is, energy in the transmission of energy from one body to another.
6. What is energy density in physics?
The quantity of energy stored in a specific system or region of space per unit volume is referred to as energy density in physics.
7. How can we increase the efficiency of the Otto cycle?
The efficiency of an Otto engine can be improved by running it on lean fuel (which consumes additional air) or by increasing the compression ratio.
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