work

(noun)

A measure of energy expended in moving an object; most commonly, force times displacement. No work is done if the object does not move.

Related Terms

  • dot product
  • angular velocity
  • rotational inertia
  • electric potential
  • force
  • electric field
  • power
  • energy

Examples of work in the following topics:

  • Negative Work and Total Work

  • Work

    • Thermodynamic work encompasses mechanical work (gas expansion, ) plus many other types of work, such as electrical.
    • As such, thermodynamic work is a generalization of the concept of mechanical work in mechanics.
    • Nevertheless, heat and work can produce identical results.
    • Both heat and work can cause a temperature increase.
    • Since pressure is constant, the work done is PΔV.
  • Kinetic Energy and Work-Energy Theorem

    • The work-energy theorem states that the work done by all forces acting on a particle equals the change in the particle's kinetic energy.
    • The principle of work and kinetic energy (also known as the work-energy theorem) states that the work done by the sum of all forces acting on a particle equals the change in the kinetic energy of the particle.
    • A force does work on the block.
    • The kinetic energy of the block increases as a result by the amount of work.
    • This relationship is generalized in the work-energy theorem.
  • Introduction to Work and Energy

    • Work is the energy associated with the action of a force.
    • An example of work is a pitcher throwing a ball.
    • Take this example of work in action from : (A) The work done by the force F on this lawn mower is Fdcosθ.
    • Work is closely related to energy.
    • Work is the energy associated with the action of a force.
  • Conservation of Energy in Rotational Motion

    • Clearly, the motor had to work to get the stone spinning.
    • Work and energy in rotational motion are completely analogous to work and energy in translational motion and completely transferrable.
    • The final rotational kinetic energy equals the work done by the torque:
    • This confirms that the work done went into rotational kinetic energy.
    • To return to the grindstone example, work was done to give the grindstone rotational energy, and work is done by friction so that it loses kinetic energy.
  • Work Done by a Variable Force

    • Integration is used to calculate the work done by a variable force.
    • Thus, a force does work when it results in movement.
    • For example, let's consider work done by a spring.
    • The SI unit of work is the joule (J), which is defined as the work done by a force of one newton moving an object through a distance of one meter.
    • Describe approaches used to calculate work done by a variable force
  • The First Law

    • The 1st law of thermodynamics states that internal energy change of a system equals net heat transfer minus net work done by the system.
    • Heat engines are a good example of this—heat transfer into them takes place so that they can do work.
    • W is the total work done on and by the system.
    • W is positive when more work is done by the system than on it.
    • Explain how the net heat transferred and net work done in a system relate to the first law of thermodynamics
  • Problem Solving with Dissipative Forces

    • In the presence of dissipative forces, total mechanical energy changes by exactly the amount of work done by nonconservative forces (Wc).
    • Since the work done by nonconservative (or dissipative) forces will irreversibly alter the energy of the system, the total mechanical energy (KE + PE) changes by exactly the amount of work done by nonconservative forces (Wc).
    • In terms of the work-energy theorem, the work done by friction (f), which is negative, is added to the initial kinetic energy to reduce it to zero.
    • The work done by friction is negative, because f is in the opposite direction of the motion (that is, θ=180º, and so cosθ=−1).
    • The most important point of this example is that the amount of nonconservative work equals the change in mechanical energy.
  • Humans: Work, Energy, and Power

    • Energy consumed by humans is converted to work, thermal energy, and stored fat.
    • Work done by a person is sometimes called useful work, which is work done on the outside world, such as lifting weights.
    • Useful work requires a force exerted through a distance on the outside world, and so it excludes internal work, such as that done by the heart when pumping blood.
    • The work going into mechanical energy is W= KE + PE.
    • Energy consumed by humans is converted to work, thermal energy, and stored fat.
  • Force in the Direction of Displacement

    • The work done by a constant force is proportional to the force applied times the displacement of the object.
    • When a force acts on an object over a distance, it is said to have done work on the object .
    • The SI unit of work is the newton-meter or joule (J).
    • Often times we will be asked to calculate the work done by a force on an object.
    • Calculate the work done on the box if the box is displaced 5 meters.
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