Lesson Plan: Instantaneous Speed | Nagwa Lesson Plan: Instantaneous Speed | Nagwa

Lesson Plan: Instantaneous Speed Physics

This lesson plan includes the objectives, prerequisites, and exclusions of the lesson teaching students how to determine the instantaneous speed of an object by using a tangent to find the gradient at a point on the object’s displacement–time graph.


Students will be able to

  • identify from straight-line displacement–time graphs what the speed of an object at a particular instant in time is (as opposed to over a time range),
  • correctly identify tangents to curves on displacement–time graphs,
  • use tangents to curves to find the speed of an object at an instant,
  • recognize that if the tangent is a horizontal line, then the speed is zero,
  • recognize that the greater the slope of the tangent, the greater the instantaneous speed at that point.


Students should already be familiar with

  • the difference between distance and displacement,
  • the difference between speed and velocity,
  • how to calculate the speed of an object from distance and time values,
  • how to calculate the velocity of an object from displacement and time values,
  • how to calculate average speeds and velocities from distance–time graphs and displacement–time graphs,
  • how to convert between common speed units.


Students will not cover

  • relating curved-line displacement–time graphs to their corresponding velocity–time graphs,
  • calculating what the tangent must be based on the function of the curve/differentiation.

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