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ZingPath: Energy, Work, and Power


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Energy, Work, and Power

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In this activity, learners will calculate the amount of work done in one and two dimensions.

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Now You Know

After completing this tutorial, you will be able to complete the following:

  • Describe that the amount of work done on an object is equal to the force applied multiplied by its displacement.
  • Explain that for work to be done on an object, the force and displacement must act in the same direction.
  • Calculate the amount of work done on an object.
  • Calculate the resultant force of a vector acting in two dimensions.
  • Describe that force is a vector quantity that represents both magnitude and direction.

Everything You'll Have Covered

In contrast with its use in everyday language, the term work in physics has a very specific meaning: mechanical work is the product of a force applied to an object and the distance the object moves in the direction of the applied force. In other words, work is equal to the applied force multiplied by the displacement due to that force. The formula for work is W = F ?x, and the unit for work is the joule (J) or newton-meter (Nm). Although energy may be used to produce a force, if that force does not result in motion (e.g., if the force of static friction is greater than the applied force, or the force acts perpendicular to an object's motion), then the work done will be zero.

If a force is applied in the same direction as the resulting displacement, then only one dimension need be considered, and the formula above suffices. Sometimes, however, the direction of the applied force differs from the direction of displacement. In such a case, the applied force may be treated as a vector in two dimensions and broken down into component forces of lesser magnitude. The resultant component force with the same direction as the displacement is then substituted into the basic equation for work.

Because a horizontal vector has no vertical component (and vice-versa), work cannot result in displacement perpendicular to the applied force. For example, holding an object and moving with it at a constant rate does not result in work because the applied force on the object is vertical (opposing gravity) while the displacement is horizontal. The work-energy theorem relates work to a change in mechanical kinetic energy of a body (W = ?K); because the object in this example moves at a constant rate, no work is being done. (However, some work is done when initially moving from standing position.)

Tutorial Details

Approximate Time 20 Minutes
Pre-requisite Concepts Define the concept of vector.Define the concept of force.Calculate the resultant for by resolving the forces into their components.Define the distance taken .Understand trigonometric properties.
Course Physics
Type of Tutorial Problem Solving
Key Vocabulary applied force, component, direction