Kinetics and Kinematics

Introduction

In our day-to-day life, we observe the motion of various objects passing in front of us. For e.g. a moving car, running animals, a ball descending downwards, people ascending to the mountains, flowing rivers, etc. 


They are in motion and would continue to move, and come at rest whenever they want to.


Physics is all time with us to deal with all such motions, and the study of the motion of these objects in simple terms called the Mechanics.


On this page, we will learn about the following: 

  • Kinetics and Kinematics

  • What is the difference between Kinetics and Kinematics?

  • Difference between Kinetics and Kinematics in tabular form

  • Difference between Kinetics and Kinematics with example

Kinetics

An arm of science that deals with the efforts (why) of forces upon the motions of material bodies or with changes in a physical or chemical system. 


Real-life examples of kinetics

You studied how the enzyme affects the rate of biochemical reactions, torque, friction.


Friction 

When a person pushes the ground backward, the rough surface of the road reacts and exerts a forward force due to friction which causes the motion without friction, the person would have slipped and wouldn’t be able to move.

Here, in the above example, kinetics is dealing with the why of motion by considering the static frictional force.


Torque

A little boy switches on the button of the toy, and the toy starts rotating around the bar. Such type of force causes the body to rotate about the fixed axis is torque.


Gas kinetics

When the jar containing the gas is put on fire, the elastic collisions start between the molecules, this is due to the production of kinetic energy during the collision, called the Brownian motion. We can say that kinetics is also used in studying thermodynamics.

Other examples

  • Polymerization

  • Nanoparticles production

  • The process for conversion of synthesis gas to hydrocarbons.

  • Combustion

  • Catalysis


Kinematics

Throw a ball, what do you see? Surely a motion, isn’t it? Kinematics is connected to the motion of any object that exists in the world, starting from the smallest particles to the largest particles in the universe and even the fastest ones, photons.

Had there been no kinematics, no one would know the motion of the earth around the Sun, neither would there be the use of Cannonballs in wars. There would be no such games such as football or cricket if you talk about the real-life experience of kinematics.

The word Kinema means motion.


Suppose you have a wooden block of some weight suppose of 8 kg and you want to see that if this block would move, what would be its position, what time and speed would it take to travel a certain distance, and the path via which it would travel either it is Parabolic, Circular or straight, but not considering why it traveled this or that path or who made that block move?


In simple terms, Kinematics describes ‘how the motion is happening’ and doesn’t take into account why the body is moving, and who is setting that body into the motion? 

Parameters in Kinematics

  • Displacement - Movement in a given direction

  • Velocity - Change in displacement: How fast an object moves in a particular direction

  • Acceleration: Change in velocity every second

  • Time - Reference for change through which the above three will be mensurated or measured.

These four variables aid you in describing the motion accurately.

Kinematics Examples

Let’s discuss a few examples by different types of motions:


Vertical Motion

Suppose you throw a stone, and you want to estimate its velocity whether there is any change in velocity or how much change is there, and the time it would take to hit the ground?


We haven’t described why that stone is descending, but only the attributes of the motion of that stone.


Horizontal Motion

Suppose you see a moving object let’s say,  a car, you would contemplate the attributes such as:

How much it traveled in meters per second?

Does the velocity change?

How much is change in the velocity?


Projectile Motion

  • Firing a cannonball  

  • Shooting a basketball

An object such as a cannonball being fired or shooting a basketball at some angle from the horizontal. It will travel some distance up into the air before descending and hitting the ground, we can use a parabola to represent the locus of these objects.

The Fundamental Differences between Kinetics and Kinematics

S.No.

Attributes

Kinetics

Kinematics

1.

Definition

Kinetics is the study of motion considering the mass and external forces as well.

Kinematics is not dependent upon the mass of the object.

2.

Relation

It attempts to determine the relationship between the motion of bodies caused by inertial force and the mass of a body. 

Kinematics is about simply describing motion. Such as velocity, displacement, time, and acceleration.

3.

Study

Study of the motion caused by forces, gravity, friction, torque

To determine the “how” of motion.

4.

Nature

It attempts to get at the cause.

It is descriptive and based on observation

5.

Treated

Treated in terms of energy transformations

Treated geometrically

6.

Example

A person sitting inside the train.

A child running around in the house, running fan

A Moving Train

Parabolic locus traced by a football.

A stone hitting the ground.

7.

Uses

Concept of gas laws, fluid dynamics, physical chemistry

Classical mechanics in terms of engineering.


FAQ (Frequently Asked Questions)

1. Why is it more difficult to catch a cricket ball than the tennis ball?

The cricket ball has a large momentum by the relation,

 momentum (a) = mass (p) x velocity (q) which states that a ∝ p. 

Since p of cricket ball > p of a tennis ball. The cricket ball will exert much larger force on the hand during catch in comparison to that of the tennis ball. That’s why it is difficult to catch the cricket ball.


2. Explain why vehicles like scooters, trains, trucks are provided with shockers?

When these vehicles move over the road, the road creates some impulsive, resistive forces in the form of jerks, so as to allow the smooth movement of these vehicles, a shocker is inbuilt within the system which absorbs all the shocks or the resistive forces caused by the uneven roads to make the smooth movement, as these shockers increase the time of impulse. This concept is also used in the trains to absorb the shocks while shunting.