Measurement of Motion

 

Subject :  Physics

Date:

Teacher:

 

 

Title:  Measurement of motion

Central Concept:   Introduction to measurement of motion

Learning Standards (National Science Education Content Standards):

B.4 - Motions and forces

A.1.4 - Formulate and revise scientific explanations and models using logic and evidence

A.1.1 - Identify questions and concepts that guide scientific investigations

 

Essential Questions:

How is motion measured?

What is the relationship between acceleration and position?

How can we measure the change in position of something that happens very rapidly?

What do graphs of constant speed and acceleration look like?

 

Content and Skills:

Develop a mathematical understanding of acceleration(B.4)

Understand methods for taking measurements of acceleration(B.4)

Scientific inquiry and reading comprehension (A.1.4, A.1.1)

 

Learning Activities:

  • Get students' definition of acceleration. What are the related concepts? Position, speed, velocity, time, distance...
  • Show video of lizard jumping. (link)Is the lizard moving?
    • How is the motion of the lizard changing?
    • Discuss details of video - the footage was taken at a rate of 500 frames per second. What does this mean? How much time passes between every frame?
  • Brainstorm: How can we measure the movement of the lizard using the video?
  • Measuring motion from a photograph:
    • High speed video can be used to measure high speed movement.
      • How can we do this? We need to be able to measure both time and distance traveled. How can we do this from the video images?
      • Measurement of time - video was shot at 500 frames per second, can we determine the time passed from this information?
      • Measurement of distance - Can we measure distance directly from the photos? Having something in the photograph of a known size, or a reference dimension, allows us measure other distances in the same photograph by comparison.
    • Manual method: In our example, we known that the distance between the tip of lizard's snout to the third dot (counting from the snout) is 60 mm. Using this dimension we can now create a grid on the photograph as is shown in this form (Lizard_Jump.pdf). In the Lizard Jump worksheet each of the images shows the time information. From this information we should be able to graph the motion of the lizard.
    • Computerized method: Using a computer and specialized software the task of measuring motion can be automated. As long as there is a clearly identifiable mark for the software to “lock” on to, programs such as Tracker can automate much of the data collection required.
      • Demonstration: Using Tracker (more information) open the Lizard_Jump.trk file. This file contains the motion tracking information along with the video of the lizard jumping.
    • This graph is a distance versus time graph of the lizard video created with a spreadsheet program using data from Tracker.
      • What can we tell from the graph?
      • What parts of the graph correspond to events in the video?

Equipment / Materials:

Internet access – projector or computer lab

Expected Outcomes:

Students should:

  1. Understand difference between instantaneous and average speed
  2. Understand how uncertainty plays a role in measuring quantities
  3. Understand the relationship between measurement uncertainty and scale of quantity measured
  4. Be able to question measurement assumptions.

 

Assessment / Assignment(s):

Homework:

Using the (Lizard_Jump.pdf) handout paper create a displacement versus time graph (either by hand on graph paper or using a spreadsheet program).