Arizona State University| PHY 121: Univ Physics I: Mechanics|Homework 1-1| Drawing a Pictorial Representation

Learning Goal:

To practice  Drawing a Pictorial Representation.
You will find that motion problems and other physics problems often have several variables and other pieces of information to keep track of. The best way to tackle such problems is to draw a pictorial representation of the problem that shows all of the important details.
  1. Draw a motion diagram. The motion diagram develops your intuition for the motion.
  2. Establish a coordinate system. Select your axes and origin to match the motion. For one-dimensional motion, you want either the x-axis or the y-axis parallel to the motion. The coordinate system determines whether the signs of v and a are positive or negative.
  3. Sketch the situation. Not just any sketch. Show the object at the beginning of the motion, at the end, and at any point where the character of the motion changes. Show the object, not just a dot, but very simple drawings are adequate.
  4. Define symbols. Use the sketch to define symbols representing quantities such as position, velocity, acceleration, and time. Every variable used later in the mathematical solution should be defined on the sketch. Some will have known values, and others are initially unknown, but all should be given symbolic names.
  5. List known information. Make a table of the quantities whose values you can determine from the problem statement or that can be found quickly with simple geometry or unit conversions. Some quantities are implied by the problem, rather than explicitly given. Others are determined by your choice of coordinate system.
  6. Identify the desired unknowns. What quantity or quantities will allow you to answer the question? These should have been defined as symbols in step 4. Don’t list every unknown, only the one or two needed to answer the question.
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