Physics HL · Chapter 1: Kinematics
How to Read This Kinematics Chapter
Set up a clean sign convention, understand what kinematics describes, and prepare for graph-based reasoning.
Estimated time: 12 minutes
What Kinematics Describes
Kinematics is the part of mechanics that describes motion without yet asking what caused it. We track position, velocity, and acceleration as a function of time, and only after we can describe motion clearly do we move on to force explanations.
That separation is useful. If your motion description is vague, force analysis becomes guesswork. If your motion description is precise, then later chapters on Newton's laws feel much more natural because each force statement can be checked against a measurable motion pattern.
Set a Sign Convention Before Solving
In one-dimensional motion, choose one direction as positive and commit to it for the full problem. The opposite direction is negative. The choice itself is arbitrary; consistency is what matters.
Negative values are not mistakes. A negative displacement tells you the final position is on the negative side of your origin. A negative velocity tells you the object is moving opposite your positive direction. A negative acceleration tells you the velocity vector is changing toward the negative direction.
Important
Most kinematics errors are sign-convention errors. Write your positive direction in words before any equations.
How This Chapter Is Organized
The chapter starts with displacement, distance, speed, and velocity in straight-line motion. It then moves to constant acceleration and the standard kinematics equations. After that, you practice graph reasoning when acceleration may vary. Finally, you model projectile motion with component methods and see how air resistance changes ideal predictions.