CBSE Class 9 || Physics || Motion || Animation || in English @digitalguruji3147

Summary

This educational script introduces the concept of motion in physics, explaining how everything moves, even if imperceptibly. It differentiates between uniform and non-uniform motion, defines speed and velocity, and introduces acceleration. The script also covers graphical representations of motion, including displacement-time graphs, and the equations of motion. It concludes with a discussion on uniform circular motion and mentions influential scientists like Isaac Newton and Johannes Kepler.

Takeaways

• 🚀 Motion is a fundamental concept in physics and refers to the change of an object's position relative to an observer.
• 📏 Motion along a straight line can be purely vertical, horizontal, or slanted, and is measured using reference points on an axis.
• 📊 Uniform motion occurs when an object covers equal distances in equal time intervals, while non-uniform motion does not.
• ⏱️ Speed is the rate of motion of an object, calculated by dividing the distance traveled by the time taken, with units of meters per second (m/s).
• ➡️ Velocity includes both speed and direction, and it is calculated similarly to speed but provides information about the object's direction.
• 📉 Acceleration is the rate of change of velocity over time, measured in meters per second squared (m/s²), and can be uniform or non-uniform.
• 📈 Graphical representations of motion, such as displacement-time and velocity-time graphs, help visualize and understand motion patterns.
• 🔄 Uniform circular motion describes an object moving at a constant speed along a circular path, with its direction constantly changing.
• ✏️ Equations of motion, such as v = u + at, s = ut + 1/2at^2, and v^2 - u^2 = 2as, help calculate various aspects of motion.
• 🪐 Examples of motion include objects like rocking chairs, swings, cars, and celestial bodies like planets and satellites in orbit.

Q & A

What is motion?

Motion is a change in the position of an object with respect to a reference point. It is one of the key concepts in physics, and everything in the universe is in motion, even if the movement is very slow or small.

How is motion related to an observer?

Motion is relative to the position of the observer. An object is considered to be in motion if its position changes with respect to the observer. For example, a car may be seen moving in relation to the ground.

What is the difference between uniform and non-uniform motion?

Uniform motion occurs when an object covers equal distances in equal intervals of time, whereas non-uniform motion happens when the object covers unequal distances in equal intervals of time.

How is speed different from velocity?

Speed is the rate of motion, defined as the distance covered per unit time. It only describes how fast an object is moving. Velocity, on the other hand, includes both speed and the direction of motion.

What is acceleration?

Acceleration is the rate at which the velocity of an object changes with time. It describes the change in both the magnitude and direction of velocity and is measured in meters per second squared (m/s²).

How is displacement different from distance?

Distance refers to the total length of the path traveled by an object, while displacement refers to the straight-line difference between the starting and final positions of the object. Displacement has both magnitude and direction.

What is the graphical representation of motion?

Motion can be represented graphically through displacement-time and velocity-time graphs. A straight line on a displacement-time graph represents uniform motion, while a curve indicates non-uniform motion. In a velocity-time graph, a horizontal line shows constant velocity, and an inclined line shows acceleration.

What are the three equations of motion?

The three equations of motion are: 1. v = u + at 2. s = ut + ½at² 3. v² = u² + 2as, where 'v' is the final velocity, 'u' is the initial velocity, 'a' is acceleration, 's' is the distance traveled, and 't' is time.

What is uniform circular motion?

Uniform circular motion refers to the motion of an object moving at a constant speed along a circular path. Although the speed is constant, the direction of motion changes continuously, so the object is still accelerating.

Can you give examples of uniform circular motion?

Examples of uniform circular motion include satellites orbiting the Earth, planets revolving around the Sun, and objects like a merry-go-round rotating at a constant speed.

Outlines

00:00

🚀 Introduction to Motion

The video starts with a mother explaining motion to her child by observing a moving object. Motion is introduced as a fundamental concept in physics, highlighting that everything in the universe moves. Even if something appears stationary, such as a person standing still, they are still in motion because the Earth orbits the sun. The mother promises to teach the child about motion in more detail at home. The learning objectives are then introduced: understanding motion, calculating speed and velocity, acceleration, and interpreting motion graphically.

05:06

🛣️ Understanding Motion and Its Types

Motion is explained as relative to the position of the observer. Different observers can perceive an object’s motion differently. Examples such as automobiles, swings, and the Earth's orbit are given to illustrate motion. The concept of motion along a straight line is introduced, explaining how even stationary objects like houses move relative to other celestial bodies. The importance of reference points in physics, along with how positions are described numerically, is emphasized. Displacement is defined as the difference between an object’s starting and final positions.

10:07

🚗 Uniform and Non-Uniform Motion

The distinction between uniform and non-uniform motion is illustrated through examples of cars moving at different rates. In uniform motion, an object covers equal distances in equal intervals of time, as shown by Car A, while Car B, which covers unequal distances in the same time intervals, represents non-uniform motion. Speed is introduced as the rate of motion, and the SI unit of speed is meters per second. The calculation of average speed is discussed, especially for objects in non-uniform motion.

15:09

💨 Velocity and Acceleration

Velocity is defined as speed with direction, distinguishing it from speed, which only measures how fast an object moves. To have constant velocity, an object must maintain both constant speed and direction. The average velocity is calculated using initial and final velocities. Acceleration, the rate of change of velocity over time, is also introduced. It is measured in meters per second squared (m/s²) and describes how quickly something speeds up or slows down. Formulas for calculating acceleration are provided.

20:09

📉 Graphical Representation of Motion

Graphs are used to represent the relationship between two sets of data. In a displacement-time graph, displacement is plotted on the y-axis and time on the x-axis. If the graph is a straight line, it shows uniform motion, while a curve represents non-uniform motion. The slope of the graph indicates the object’s velocity. Additionally, distance-time graphs and velocity-time graphs are introduced, demonstrating how they can visually depict the motion of objects, including constant speed, acceleration, and deceleration.

📐 Equations of Motion

The three key equations of motion are discussed, each representing different aspects of velocity, distance, and time for objects moving with uniform acceleration. The first equation links velocity, acceleration, and time. The second equation describes the relationship between distance traveled, initial velocity, and time. The third equation connects position and velocity. These equations help calculate important variables in motion and are explained through graphical methods and examples.

🔄 Uniform Circular Motion

The concept of uniform circular motion is explored, where an object moves in a circular path at a constant speed. Even though the object’s speed remains constant, its direction constantly changes. Examples such as a merry-go-round, satellites orbiting Earth, and planets around the Sun are given. Newton's contributions to the laws of motion and planetary motion are briefly introduced.

📜 Summary of Motion Concepts

The lesson concludes by summarizing key concepts: motion is a change in position and can be uniform or non-uniform. Speed measures the distance covered per unit time, while velocity accounts for displacement. Acceleration is the rate of change of velocity. Graphs can represent motion, and the three equations of motion describe objects moving with uniform acceleration. Lastly, uniform circular motion describes objects moving at constant speed in a circular path.

Keywords

💡Motion

Motion refers to the change in position of an object over time. In the video, it is introduced as a fundamental concept in physics that applies to everything in the universe, whether it is visible movement like a car or less obvious, like the Earth orbiting the Sun. The video explains that motion can be along a straight line, circular, uniform, or non-uniform.

💡Uniform Motion

Uniform motion occurs when an object moves at a constant speed, covering equal distances in equal intervals of time. In the video, the example of Car A moving 10 meters every 5 seconds demonstrates uniform motion, illustrating that this type of motion involves consistent velocity without acceleration.

💡Non-uniform Motion

Non-uniform motion is when an object covers unequal distances in equal intervals of time, meaning the object's speed varies. The video illustrates this concept using Car B, which covers 5 meters in 5 seconds and then 15 meters in the next 5 seconds. This variation in speed shows how non-uniform motion is characterized by changing velocity.

💡Speed

Speed is the rate at which an object moves over a distance within a specific period of time. It is a scalar quantity that measures how fast something is moving, without considering its direction. In the video, speed is introduced as the distance traveled per unit of time, with the formula speed = distance/time.

💡Velocity

Velocity is a vector quantity that measures the speed of an object in a specific direction. Unlike speed, velocity includes both magnitude and direction, making it more descriptive. The video explains that for velocity to be constant, both the speed and the direction of an object's motion must remain the same. It also presents average velocity as the arithmetic mean of initial and final velocity.

💡Acceleration

Acceleration is the rate at which an object's velocity changes over time. It can describe both speeding up and slowing down (deceleration). The video defines it as a measure of how quickly an object’s velocity changes and provides the formula: acceleration = (final velocity - initial velocity) / time. The concept is further explained using examples like the motion of a racing car.

💡Displacement

Displacement is the shortest distance from an object's initial position to its final position, including direction. It differs from distance because it considers direction, making it a vector quantity. The video gives examples of how displacement is used in physics to describe an object's overall change in position, such as when comparing a car's starting and ending points.

💡Graphical Representation of Motion

Graphical representation of motion refers to the use of graphs to visualize an object's motion over time. The video introduces displacement-time and velocity-time graphs to help explain different types of motion. For instance, a straight line on a displacement-time graph indicates uniform motion, while a curve indicates non-uniform motion. These graphs also help visualize acceleration and constant speed.

💡Uniform Circular Motion

Uniform circular motion refers to the movement of an object along a circular path at a constant speed. The video explains that while the speed remains constant, the object is continuously changing direction. Examples provided include the Earth's orbit around the Sun and satellites orbiting Earth. The constant change in direction makes it distinct from linear motion.

💡Newton's Laws of Motion

Newton’s Laws of Motion describe the relationship between the motion of an object and the forces acting on it. Although not detailed in the video, it mentions Isaac Newton’s contributions, such as the three laws that govern motion, laying the foundation for much of classical physics. These laws help explain everyday phenomena like why objects remain at rest or in motion unless acted upon by a force.

Highlights

Motion is one of the key topics in physics, and everything in the universe moves, even if it's very slow or small.

Motion is relative to the position of the observer. An object is in motion if its position changes with respect to an observer.

Motion along a straight line can be purely vertical, horizontal, or slanted, but it must follow a straight path.

Position is marked by a unit of length, such as meters, and distance is the magnitude of movement regardless of direction.

The difference between an object's starting position and final position after it moves is known as displacement.

Uniform motion means an object covers equal distances in equal intervals of time, while non-uniform motion means the distances vary over time.

Speed is the rate of motion, involving both distance and time, and its SI unit is meters per second.

Velocity describes both speed and direction of an object. It's the same as speed but includes direction, and the formula is similar.

Acceleration is the rate of change of velocity over time and is measured in meters per second squared.

Graphical representation of motion helps visualize how displacement, speed, and acceleration change over time using distance-time and velocity-time graphs.

The slope of a displacement-time graph represents the velocity of an object, while the slope of a velocity-time graph shows its acceleration.

Three key equations of motion help calculate velocity, distance, and acceleration, such as v = u + at and s = ut + 1/2 at².

Uniform circular motion occurs when an object moves along a circular path at constant speed, such as planets orbiting the sun.

Uniform circular motion constantly changes direction, even though speed remains constant.

Sir Isaac Newton contributed significantly to our understanding of motion with his three laws, which connect forces to the motion of bodies.

Transcripts

introduction

see mom that joint wheel that is moving

yes that giant wheel is in motion

what is motion mom

motion is one of the key topics in

physics

everything in the universe moves

how

it might only be a small amount of

movement

and very very slow

but movement does happen

but i am not in motion

even if you appear to be standing still

the earth is moving around the sun

and the sun is moving around our

galaxy mom i want to know more about

motion please tell me

okay let's go home

i will teach you about motion

objectives

at the end of this lesson you'll be able

to

define motion

describe motion along a straight line

understand uniform and non-uniform

motion

calculate speed

define and calculate velocity

define acceleration

understand the graphical representation

of motion

explain uniform circular motion

understanding motion

motion is relative to the position of

the observer

for example you can see that an

automobile is moving with respect to the

ground

different observers may perceive the

motion of an object in entirely

different way

or we can say that an object is in

motion if its position changes with

respect to an observer

a rocking chair a swing a bouncing ball

are the examples of things that assist

motion

the earth in its orbit around the sun is

also said to be in motion

motion along a straight line

everything in a world moves

even stationary things such as your

house move in relation to the sun or to

the other stars

the motion may be purely vertical that

of a falling stone purely horizontal

that of a car on a level highway or

slanted that of an airplane rising at an

angle from a runway but it must be a

straight line

when we try to locate an object in

physics we will usually relate it to

some sort of reference point

this point is usually the origin the

zero point of an axis x y or z

furthermore we provide a numeric

representation for an object's location

by placing it either in the positive

direction or negative direction in

relation to that reference point

for example let's put a particle at x is

equal to 10 meters

the particle would then be located at 10

meters from the origin on the x-axis

as you may have noticed position is

marked by some unit of length

the typical unit we will use is meters

here the distance covered by the object

is 10 meters

to describe distance we need to specify

only the numerical value and not the

direction of motion

the numerical value of a physical

quantity is its magnitude

the difference between an object's

starting position and final position

after it moves is known as displacement

uniform motion and non-uniform motion

to understand uniform and non-uniform

motion let's take one example

look at this table

this is the distance covered by a car a

we can see that in zero seconds it

covers zero meters

in five seconds it covers 10 meters

in 10 seconds it covers 20 meters and so

on

or we can say that in every 5 seconds it

covers 10 meters

it travels equal distances in equal

intervals of time

hence it is in uniform motion

look at carbena

carb covers 5 meters in 5 seconds 15

meters in 10 seconds

20 meters in 15 seconds

we have seen that the car b does not

cover equal distances in equal intervals

of time therefore it is in non-uniform

motion

speed

now can you tell the difference between

two identical objects traveling at

different speeds

nearly everyone knows that the one

moving faster or the one with a greater

speed will go farther than the one

moving slower in the same amount of time

whatever speed is it involves both

distance and time

faster means either farther great

distance or sooner less time

doubling one speed would mean doubling

once distance traveled in a given amount

of time

doubling one speed would also mean

halfing the time required to travel a

given distance

the rate of motion of an object can be

measured by finding out the distance

traveled by the object in unit time

the si unit of speed is meter per second

this is represented by this symbol

in most cases objects will be

non-uniform motion therefore we describe

the rate of motion of such objects in

terms of their average speed

the average speed of an object is

obtained by dividing the total distance

traveled by the total time taken

if an object travels a distance s in

time t then its speed v is

v is equal to s upon t

speed with direction

velocity is speed in a given direction

speed describes only how fast an object

is moving whereas velocity gives both

the speed and direction of the object's

motion

to have a constant velocity an object

must have a constant speed and motion in

a constant direction

it is calculated in the same way as we

calculate average speed

it is given by the arithmetic mean of

initial velocity and final velocity for

a given period of time

that is average velocity is equal to

initial velocity plus final velocity by

two

where v av is the average velocity

u is the initial velocity and v is the

final velocity of the object

speed and velocity have the same units

that is meter per second

rate of change of velocity

acceleration is the rate of change of

velocity with time

in one dimension acceleration is the

rate at which something speeds up or

slows down

acceleration describes the rate of

change of both the magnitude and the

direction of velocity

in si units acceleration is measured in

meters per second square

it is a measure of the change in the

velocity of an object per unit time

that is acceleration is equal to change

in velocity by time taken

if the velocity of an object changes

from an initial value u to the final

value v in time t

the acceleration a is

v minus u upon t

uniform or constant acceleration is a

type of motion in which the velocity of

an object changes by an equal amount in

every equal time period

on the other hand an object can travel

with non-uniform acceleration if its

velocity changes at a non-uniform rate

example

let us take the example of a racing car

it takes 10 minutes or 0.17 hours to

travel 23 kilometers from start to

finish

we have to find the average speed and

average velocity

we know that average speed is distance

traveled by time taken

therefore average speed is equal to 23

kilometers by

0.17 hours which is equal to

135.29 kilometers per hour

similarly average velocity is

displacement by time taken

we can see in the picture that

displacement is four kilometers

therefore average velocity is equal to

four kilometers by 0.17 hours which is

equal to

23.53 kilometers per hour

graphical representation of motion

a graph is a pictorial representation of

the relation between two sets of data of

which one set is of dependent variables

and the other set is of independent

variables

in a displacement time graph

displacement is a dependent quantity

taken on the y-axis and time is taken on

the x-axis as it is independent

if the position of an object changes

with time it is said to be in motion

if an object has equal displacements in

equal intervals of time then the graph

is a straight line inclined with the

x-axis which represents uniform motion

of the object

if the graph is a curve it represents

non-uniform motion

the slope of displacement time graph

gives velocity of the object

we will go through this in detail after

a short interactivity

distance time graphs

plotting distance against time can tell

you a lot about motion

let's look at the axis

time is always plotted on the x-axis

bottom of the graph the further to the

right on the axis the longer the time

from the start

distance is plotted on the y-axis side

of the graph

the higher the graph the further from

the start

if an object is not moving a horizontal

line is shown on a distance time graph

we can see that the time is increasing

to the right but its distance does not

change

it is not moving

we say it is at rest

if an object is moving at a constant

speed it means it has the same increase

in distance in a given time

in the graph we can see that time is

increasing to the right and distance is

increasing constantly with time

this means the object moves to a

constant speed

constant speed is shown by straight

lines on a graph

velocity time graphs

velocity time graphs are also called

speed time graphs

speed time graphs look much like

distance time graphs

time is plotted on the x-axis speed of

velocity is plotted on the y-axis

a straight horizontal line on a

speed-time graph means that speed is

constant it is not changing over time

this graph shows increasing speed the

moving object is accelerating

this graph shows decreasing speed

the moving object is decelerating

this is a velocity time graph of an

object in non-uniformly accelerated

motion

equations of motion by graphical method

the three equations of motion are

v is equal to u plus a t

s is equal to u t plus one upon two a t

square

two a s is equal to v square minus u

square

we use the initial velocity of the

object which moves with uniform

acceleration a for time t

v is the final velocity and s is the

distance traveled by the object in time

t

this equation describes the velocity

time relation

this equation represents the position

time relation

this represents the relation between the

position and the velocity and can be

obtained from these two equations

let us go through them one by one

equation for velocity time relation

consider an object moving with a uniform

velocity u in a straight line

let it be given a uniform acceleration a

at time t is equal to 0 when its initial

velocity is u

as a result of the acceleration its

velocity increases to v final velocity

in time t and s is the distance covered

by the object in time t

the figure shows the velocity time graph

of the motion of the object

slope of the vt graph gives the

acceleration of the moving object

thus acceleration is equal to slow which

equals av which equals bc upon ac which

is equal to v minus u whole upon t minus

o

where a is equal to v minus u

whole upon t

this equals v minus u equal to 80.

v equals u plus 80 which is the first

equation of motion

equation for position time relation

let the distance traveled by an object

is s in time t and acceleration a

we can see that the distance traveled by

the object is obtained by the area

enclosed within

therefore distance traveled s is equal

to area of the trapezium abdo

which equals area of rectangle acdo

plus area of triangle abc

which is equal to od into oa plus one

upon two bc into ac

now putting the values we get t into

u plus 1 upon 2 into

v minus u

into t

on solving further we get ut plus 1 upon

2 into v minus u into t

now from the first equation we know that

v minus u is equal to 80 or we can write

v is equal to u plus 80.

therefore s is equal to ut plus 1 upon 2

80 square

this is the second equation of motion

equation for position velocity relation

the third equation will be obtained from

these two equations

from the velocity time graph distance

traveled s is equal to area of the

trapezium oabt

this is 1 upon 2 into

b1 plus b2 whole into h

which is equal to 1 upon 2 into oa plus

bd whole into ac

substituting oa by u

b d by v

and ac by t we get s is equal to 1 upon

2 into u plus v whole into t equation 1

but we know that a is equal to v minus u

whole upon t

or t is equal to v minus u whole upon a

substituting the value of t in equation

one we get

v square minus u square is equal to two

a s

two a s is equal to

v plus u into v minus u

v plus u into v minus u is equal to 2 a

s

by using the identity a square minus b

square is equal to a plus b into a minus

b we can't

v square minus u square is equal to 2 a

s

this is the third equation of motion

uniform circular motion

uniform circular motion describes the

motion of a body traversing a circular

path at a constant speed

the distance of the body from the axis

of rotation remains constant at all

times

as an object moves in a circle it is

constantly changing its direction

merry-go-round is an example of uniform

circular motion

satellites orbiting our earth artificial

satellites or our moon have emotions

that are very nearly uniform circular

motion

the planets that orbit our sun have

motions that are very nearly uniform

circular motion

did you know

sir isaac newton is one of the most

influential scientists of all time

he came up with numerous theories and

contributed ideas to many different

fields including physics mathematics and

philosophy

born in england isaac newton was a

highly influential physicist astronomer

mathematician philosopher alchemist and

theologian

newton's three laws of motion relate the

forces acting on a body to its motion

john scapler helped lead a scientific

revolution in the 17th century with his

amazing work in the field of astronomy

among his many contributions were the

three laws of planetary motion

summary

let us summarize what we have learned

motion is a change of position

it can be described in terms of the

distance moved or the displacement

the motion of an object could be uniform

or non-uniform depending on whether its

velocity is constant or changing

the speed of an object is the distance

covered per unit time and velocity is

the displacement per unit time

the acceleration of an object is the

change in velocity per unit time

uniform and non-uniform motions of

objects can be shown through graphs

the motion of an object moving at

uniform acceleration can be described

with the help of three equations namely

v is equal to u plus 80

s is equal to u t plus 1 upon 2 a t

square

2 a s is equal to v square minus u

square

where u is initial velocity of the

object which moves with uniform

acceleration a for time t

v is its final velocity and s is the

distance it traveled in time t

if an object moves in a circular path

with uniform speed its motion is called

uniform circular motion

[Music]

you