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Main Kinematics & Dynamics Understanding Motion Lesson I.1.1 Unit I:Kinematics & Dynamics

Understanding Motion - Lesson I.1.1

Key Terms: Physics | Kinematics | Motion | Reference Point | Uniform motion | Non-uniform motion| Stroboscope CELS: IL, CCT

Physics: Our Physical World

Physics is relevant to us all. It allows us to analyze and appreciate our ever changing environment. Throughout this site you will notice that Physics has a foundation in mathematics but also involves ideas, principles and laws that can be expressed in words.

Problem solving in physics should be completed in a systematic, organized and logical manner. It is necessary to have this structured approach when solving any type of problem in any of the sciences.

Problem Solving Strategy
  1. Read the problem carefully and list the important information with symbols and units. Make a sketch of the situation if necessary.
  2. Identify the unknown quantity.
  3. Write down the appropriate equation.
  4. Substitute the numerical values and units into the equation and solve.
  5. Include the answer as part of a final statement.
A large branch of Physics is called Mechanics. This is broken down into two smaller branches; that of kinematics and dynamics. Kinematics describes the motion of an object where as dynamics involves a description of motion and the forces behind it (the "why").
Mechanics -->Kinematics & Dynamics

We will first look at the branch of physics called kinematics. Since kinematics involves the description of motion we must be very clear about what motion is.

    It is:
  • the movement of an object from one place to another
  • measured over a time interval such as s, min, h
  • relative to the position of the observer or the reference point
Example of
non-uniform motion:
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Why is this an example of non-uniform motion?

Show Answer


Flash MovieWatch the movie

If the reference point is determined to be the initial position of the sheep, then as the sheep runs to its owner it is moving away from the reference point. You could also describe his motion as moving toward the owner or the observer. If a coyote now looks out from behind a bush and sees the sheep, the coyote becomes an observer and the motion of the sheep is away from this observer.

You may have experienced looking out your car window at the vehicle beside yours. Thinking that the vehicle beside you is stationary and it is actually moving, you think you are in motion. You quickly hit the brakes as a reaction to the perception of motion. In actuality you are stopped and the car beside you is in motion. The observer on the sidewalk sees that your vehicle is stationary and the vehicle beside you is moving.

Now that we understand what motion in general is, we want to be more specific.

What is Uniform Motion?

Uniform Motion

What is Non-uniform Motion?

Non-uniform Motion

Motion #2

After examining the graphics, take a moment to write down the differences between these two types of motion.

Periodic motion is a unique type of non-uniform motion. It is a motion that repeats itself over a period of time. The most common type of periodic motion is the pendulum. Rapid periodic motion can be analyzed with a stroboscope. This instrument allows you to view frames of movement which appears to visually slow the motion of an object.


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