1. What Is Kinematics?
Kinematics is the study of how objects move. It focuses only on describing motion and does not worry about why the motion happens. That means we do not look at forces like push or pull here. We simply observe and describe what we see.
For example, when you watch a car moving on the road, kinematics helps you talk about how fast it is going, how far it has travelled, and how its speed changes with time.
1.1. Why Do We Need Kinematics?
Kinematics makes it easier to understand motion before learning the causes behind it. It gives a clear picture of concepts like distance, time, speed, and acceleration.
If we try to jump directly to forces, it becomes confusing. So we first describe motion in a simple and systematic way.
2. Basic Terms Used in Kinematics
To describe motion clearly, we use some common terms. These terms help us discuss motion in a scientific way.
2.1. Distance and Displacement
Distance is the total path covered by an object. It does not depend on direction.
Displacement is the shortest straight-line distance from the starting point to the ending point. It has both magnitude and direction.
2.1.1. Simple Example
If you walk 10 meters forward and then 10 meters back, your distance is 20 meters, but your displacement is \(0\) meters because you end up at the same point where you started.
2.2. Speed and Velocity
Speed tells us how fast an object is moving. It does not consider direction.
Velocity is speed in a particular direction. It can be positive or negative depending on direction.
2.2.1. Speed and Velocity Formula
The basic formula for speed or velocity is:
\( \text{Speed/Velocity} = \dfrac{\text{Distance or Displacement}}{\text{Time}} \)
2.3. Acceleration
Acceleration tells us how quickly the velocity of an object changes. If a vehicle speeds up or slows down, it is accelerating.
2.3.1. Acceleration Formula
Acceleration is calculated as:
\( a = \dfrac{v - u}{t} \)
where \(u\) is initial velocity, \(v\) is final velocity, and \(t\) is time taken.
3. Types of Motion in Kinematics
In kinematics, we mainly deal with three simple types of motion. Understanding these helps us describe motion more accurately.
3.1. Uniform Motion
An object is in uniform motion if it covers equal distances in equal intervals of time. Example: a car moving at a steady speed of 40 km/h.
3.2. Non-Uniform Motion
An object is in non-uniform motion when it covers unequal distances in equal intervals of time. Example: a bike moving in city traffic.
3.3. Rest
An object is in rest if it does not change its position with time relative to its surroundings. Example: a book kept on a table.
4. How Kinematics Describes Motion
Kinematics uses graphs, equations, and simple measurements to describe how motion changes with time. We do not look at forces like gravity or friction here. We only measure motion.
4.1. Position-Time Graphs
A position-time graph shows how the position of an object changes over time. A straight line means uniform motion.
4.2. Velocity-Time Graphs
A velocity-time graph helps us understand how velocity changes with time. The slope of this graph gives acceleration.
5. Kinematic Equations of Motion
When acceleration is constant, we can use three important equations to describe motion. These are known as the equations of motion.
5.1. The Three Equations
- \( v = u + at \)
- \( s = ut + \dfrac{1}{2}at^2 \)
- \( v^2 = u^2 + 2as \)
These help us solve problems related to moving objects.