CHAPTER 1: LINEAR MOTION

Linear motion is the most fundamental type of motion—movement along a straight line. Everything from a car speeding down a highway to an apple falling from a tree obeys the laws described in this chapter. Master this, and you master the language of mechanics.

1.1 DISPLACEMENT, VELOCITY, AND ACCELERATION

Before we can analyze motion, we must define the tools we use. These are not just words; they are precise, measurable quantities.

1.1.1 Displacement (s)

• Definition: Displacement is the distance moved in a specified direction. It is the straight-line distance from an object's starting point to its ending point, with an arrow pointing from start to finish.
• Scalar vs. Vector: Displacement is a vector quantity (it has both magnitude and direction). Distance is a scalar (it only has magnitude).
• Symbol: s (sometimes x or y)
• SI Unit: metre (m)
• Example: If you walk 5 km North, your displacement is 5 km North. If you walk in a circle and return to your start, your displacement is ZERO, even though you walked a long distance.