Motion in a Straight Line
2.1 Introduction
Motion is everywhere! From walking and cycling to blood flowing in our bodies, leaves falling, and even the Earth moving around the Sun—everything is in motion. Motion means an object’s position changes over time. In this chapter, we’ll focus on rectilinear motion, which is motion along a straight line.
We’ll learn how to describe motion using:
- Velocity (how fast something moves and in what direction).
- Acceleration (how quickly velocity changes).
We’ll also study special cases where acceleration is constant, making the math simpler. Plus, we’ll explore relative velocity, which helps us understand motion from different perspectives.
To keep things simple, we’ll treat objects as point-like (ignoring their size) when the distance they travel is much larger than their actual size. This works well for many real-world situations.
Fun fact: This chapter is part of Kinematics—the study of motion without worrying about what causes it (that’s for later chapters!).
Key Equations (Preview)
Later, we’ll use these for motion with constant acceleration:
- \( v = u + at \)
- \( s = ut + \frac{1}{2}at^2 \)
- \( v^2 = u^2 + 2as \)
Where:
\( u \) = initial velocity,
\( v \) = final velocity,
\( a \) = acceleration,
\( s \) = distance,
\( t \) = time.
Important Concepts for NEET
Here are 3 must-know ideas from this section that often appear on exams:
- Rectilinear Motion: Motion along a straight line (e.g., a car moving on a straight road).
- Instantaneous Velocity: An object’s speed and direction at a specific moment in time.
- Uniform Acceleration: When an object’s velocity changes at a constant rate (simplifies calculations).
- Relative Velocity: How the velocity of one object appears from another moving object’s perspective.
- Point Object Approximation: Treating objects as tiny points when their size doesn’t affect the motion description.
Keep these in mind—they’re the foundation for solving problems in this chapter!
