The joule is the SI unit of labor (J). A joule is defined as the work done by a force of one newton creating a one-meter displacement. Work is sometimes measured in newton-metres (N-m). One J = 1 N-m.

There are several ways to classify and measure work. The three most common methods are: rate times time, power, and energy. They all relate work to energy but they define it in different ways so that each method can be used to compare results between experiments or objects with different properties. For example, power is the product of force and velocity, so if we doubled the force but kept the velocity the same, the work done would double. Energy is always changing things; it is never still. Work is energy change; therefore, it can be thought of as the capacity of a system to do **useful work**.

Work is often called "useful" work because any energy transfer causes changes in the state of the involved systems. In other words, work is the transport of energy from one place to another. We will now look at some examples of work in daily life. Let's say you push a cart down a hill. This works because you are using your muscles and they experience stress as they try to resist your push. That is what makes your muscle cells work - to provide resistance for the movement of the cart.

Joule The SI unit of labour is the joule (J), which is also the unit of energy... Tasks (physics)

Work | |
---|---|

Common symbols | W |

SI unit | joule (J) |

Other units | Foot-pound, Erg |

In SI base units | 1 kg⋅m2⋅s−2 |

The joule (symbol J) is the SI unit of energy, and it measures the ability to accomplish work or create heat. One joule is equal to the work done (or energy wasted) by a force of **one newton** (N) acting over a one-meter distance (m). As a result, one joule is equivalent to one newton*meter.

Because work is the product of force and distance, it makes sense that we should use meters as our basic unit of work measurement. And since force is mass times acceleration, it follows that our basic unit of energy should be the meter per second squared (m/s2). Combining **these two concepts**, we can say that one joule is equal to **one newton meter** per **second square**.

In practice, however, humans generally express energy in kilojoules (kJ), which is 1000 joules. A kJ is therefore equivalent to 1 newton meter per second square. It is important to remember this relationship when dealing with energies that are not measured in joules.

For example, when talking about the energy needed for something such as heating or cooling, people often use degrees Celsius or Fahrenheit as units. These units are based on the temperature of water, and 1 degree Celsius is like one tenth of a degree Fahrenheit. Therefore, 1 degree Celsius is really just 1/10 degree Fahrenheit.

Energy and work are measured using the same units because they are two sides of the same coin. The joule (J) is the SI unit of energy and work, named after the English scientist James Prescott Joule (1818–1889). A J is equal to 1 newton meter (N m or kg m2/s2), which is the standard unit for **mechanical power**.

In general practice, it does not matter which unit you use as long as you are consistent. For example, you could say that water energy is about 2.5 megajoules (Mj) per kilogram (kg), but that also means that it takes about 2.5 Mj to lift one kilogram (1 kg) about one meter (m).

There are other ways to express energy than in J/kg or Mj. For example, there is chemical energy, which is expressed in ergs per mole; thermal energy, which is expressed in calories per degree Celsius (°C); and light energy, which is expressed in photons emitted by a candle over time. All these forms of energy are equivalent to each other and can be converted into one another.

The word "work" has several different meanings in physics. In this context, we are only interested in mechanical work.

The Newton metre is also known as the Joule metre, after James Joule, the greatest scientist of all time. In this case, the unit of work is derived with the assistance of other fundamental units. As a result, a unit of work is a derived unit.