The chapters we need to study in kinematics

The chapters involved in the study of kinematics are:

1. Vectors and Scalars
2. Motion in One dimension
3. Motion in two dimensions ( Projectile motion)

Vectors and Scalars :

The study of Kinematics starts with the concept of Vectors and Scalars.

In this chapter we define different quantities depending on their definition. Like few quantities which can be defined just with their magnitudes like distance, speed, work etc. These quantities are called Scalar quantities. On the other hand few quantities can be defined with the help of their magnitude and direction and they are called Vector quantities like displacement, velocity, force etc.

Now, we can perform mathematical operations (addition, subtraction, multiplication and division) for both these quantities and the process for each is different. For scalar quantities we can do the operations just the way we have been doing in the algebraic operations. Whereas for vector quantities, it is not possible to do it by that method. For addition we use Parallelogram law or triangle law or polygon law of vector addition. For multiplication there are two types- Scalar ( dot ) product and Vector ( cross ) product (taught in class 11th). So, these operations which we are performing are for all the vector quantities like velocity, displacement, force etc. We just simply can't add them. 

Along with these we should be familiar with different algebraic results and basic calculus understanding ( for class 11th ).

These were some of the basic concepts which we needed to learn before entering into the Kinematics.

Before moving further with Kinematics, let us first understand what do we study in kinematic? What is Kinematics all about?

Kinematics :

👉 Kinematics is all about studying the state of rest or motion of any object without taking care of what caused the object to come into motion or to rest. The reasons will be studied in detail in the dynamics chapter.

Bunny - Sir, what comes under the state of rest or motion? Please explain me in detail.

Simplified Physics - Sure.... 

Just stand at a place in a market and look all around you.

What do you see?

Bunny - People, bikes, bi-cycles, autos...

Simplified Physics - Are all in the same state? I mean are they all at rest? or all in motion?

Bunny - No sir few people are walking down the road and few are standing in front of the store. I can see few bikes running and few parked in the parking area.

Simplified Physics - What else do you see? are all the moving objects having the same velocity?

Bunny - No Sir .. Not at all.. few are moving slowly and few are faster. Few are slowing down and few are speeding up. Their state of motion are not at all same.

Simplified Physics - Excellent observation Bunny. This is what we are going to study in kinematics. We will be studying about the state of motion or rest of different objects. We will be determining how far they will go in a particular time? How much will a car move after the brakes are applied before the car stops.

Bunny - Great, Its very interesting. Please tell me more about it.

Simplified Physics - Sure.

Now, let's move further. When we study the state of motion of any object, we define the dimensions. Like we define whether the motion is in One Dimension, or Two Dimensions or Three dimensions. For class 9, we concentrate only on One Dimension motion. For class 11, we learn about One and Two dimensions of motion. Two dimensional motion is termed as Projectile motion. There we study about any particle thrown from one place on the ground to another place.

In kinematics, we not only learn about the uniform motion of bodies but also the motion in which the velocity is constantly increasing or constantly decreasing. We also study about the motion of any object with respect to another object. The objects may be in motion or rest.

We also come across a term called frame of reference. Frame of reference is the observer who observes and defines the state of motion or rest of an object. Let's try to understand this with a very simple example: Suppose you are standing inside a train and your friend is standing on a platform. Currently the train is at rest. So, your friend will see that you are also at rest. All other passengers around you will also observe that you are at rest. Now, if the train starts to move, your friend will see that you are also moving along with the train. But will the passengers around you will also see you moving? No... they will see that you are standing still just as before.

What do you observe here?

It is observed that with respect to different observers our state of rest or motion is different. For one I am at rest and for others I am in motion. This is called frame of reference. All these observers are different frame of references. So, Frame of reference is anything with respect to which we can define any object's motion.

After we understand frame of reference, then we understand the concept of Relative velocity. Relative velocity is the velocity of any object with respect to any other body or the observer or the frame of reference anything we can say. Using this concept we will understand different vehicle overtaking problems that we come across. 

So, these were certain concepts we learn in the chapter kinematics. Now, Let me tell you something about the projectile motion. In this chapter, we study about the motion of any particle which is moving on a plane. For example, a ball thrown in air. We can determine how high the ball will go and how far from the point of projection. We often use this concept while playing cricket. we throw the ball in air and the ball reaches the wicket keeper.

Simplified Physics: So Bunny, I hope you understood the motive behind studying the kinematics.

Bunny: Thanks a lot sir.