What is Motion in Physics?

October 7, 2023October 7, 2023

Hello friends,

In this post, we are going to explore ‘What is Motion in Physics?’. Motion is all about things moving or changing their position. Whether it’s a car zooming down the road or the planets in the sky, everything around us experiences motion in one way or another. Understanding motion helps us describe and predict how objects move, making it a fundamental concept in science and our daily lives. We are going to know about different types of motion, speed & velocity, and many other topics which is going to make our journey stimulating. So let’s dive into this matter.

What is Motion in Physics?

Motion is simply the act of something moving, like a bicycle rolling down the street or a bird flying through the sky. It’s what happens when an object changes its location or position over time. Motion is a fundamental concept in physics, helping us understand how things move and interact with one another in our world. Whether it’s a car racing on a track or a soccer ball being kicked into the goal, motion is all about how objects change their position, and it’s a crucial idea in the study of the physical world.

REST AND MOTION CONCEPT (What is Motion in Physics?)

Rest and motion are fundamental concepts in physics that describe the state of an object. When an object is at rest, it means it’s not moving; it’s staying still. Think of a parked car – it’s not going anywhere; it’s at rest. On the other hand, motion refers to when an object is moving from one place to another. When a car is driving down the road, it’s in motion because it’s changing its position.

TYPES OF MOTION IN PHYSICS

Distinct objects can possess several different style of manner to conduct their motion. An entity can acquire two or more types of motion at a particular time. Let us read further to get into the hidden depths of this topic.

1. TRANSLATORY MOTION

An object moving in such a manner that every part of that object moves the same distance in the same time is translatory motion. It has three types:

a) Rectilinear motion: the motion an object on a straight path is called rectilinear motion. For example: an apple falling from tree, a car moving on a straight road, a snooker ball being hit (billiards game).

b) Curvilinear motion: the motion of an object on a curved path is called curvilinear motion. For example: a ball being hit at an angle, a javelin throw, earth moving around sun.

c) Circular motion: It is a special case of curvilinear motion. The object moves on a closed curve path in which the distance of the object from the fixed point always remains the same. For example: a child sitting on a giant wheel/merry-go-round.

2. ROTATORY MOTION

An object rotating or spinning on its axis only (axis of rotation), it is called rotatory motion. Additionally, when an object is in rotatory motion, all the parts of the object do not move the same distance in the same time interval. Have this means that the part away from the axis moves greater distance in less time than the part near the axis.

For example: a 360º movable chair, a spinning top, wheel of a car, rotation of clock hands, spinning of potter’s wheel.

3. OSCILLATORY MOTION

The motion of the object falls under a to-and-fro pattern from its mean position (rest position). For example: swinging pendulum of wall clock, a child moving to-and-fro on a swing.

a) Vibratory motion: When only some part of an object moves to-and-fro, not the whole body, it is considered vibratory motion. Therefore, vibratory motion is called a special case of oscillatory motion. For example: prongs of a tuning fork, hitting/plucking strings of a guitar.

4. REPETITIVE MOTION

When an object repeats its motion in certain intervals of time, it is considered a repetitive motion. It may occur periodically (at regular intervals) or non-periodically (at any time).

a) Periodic motion: It is a type of repetitive motion which repeats itself at regular intervals of time (fixed). For example: earth taking a complete revolution of the sun , clock pendulum to-and-fro motion (oscillation).

b) Non-periodic motion: It is a type of repetitive motion which can occur at any point of time (not fixed). For example: motion of arms and legs while walking, breathing depends (motion of lungs changes), motion of a rolling ball, oscillating of tree branches.

5. RANDOM MOTION

When an object chooses a random or an irregular path for its motion, such that it repeatedly changes its direction or speed, it is listed under random motion. For example: a butterfly flying in an irregular path, a football/badminton player changing its speed and direction frequently, a dancer altering its speed and direction in order to change its steps.

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COMBINATION OR MULTIPLE MOTION

There can be an example of motion in daily life which falls under two or more categories of motion. Hence we can say that, an entity that possesses two or more types of motion is called a combination motion or multiple motion.

For example:

Drilling machine → rectilinear motion (it moves straight), rotatory motion (it rotates in its own axis).
Earth revolving around Sun → rotatory motion (earth moves on its axis), curvilinear motion (a curve forms when earth revolves around the Sun), periodic motion (revolution of earth occurs periodically).
Car wheels → rotatory motion (wheel moves on its axis), translatory motion (wheels can move on a straight or a curved path).
Bowling by a bowler → rotatory motion (ball is spinning when bowled), translatory motion (the ball reaches the batsman in straight or curve manner).
Swinging pendulum of wall clock → oscillatory motion (pendulum moves to-and-fro), repetitive motion (periodic motion: occurs at regular intervals).

ENERGIZER! (‘What is Motion in Physics?’)

Identify the types of motion and list them at the correct places in the table below.

Motion of your hands while running
Motion of a boy sitting on a merry-go-round
Motion of a train on a straight track
Movement of the lungs during breathing
Revolution of the earth around the sun
Motion of a butterfly
Motion of a horse pulling a cart on a straight road
Swinging pendulum of a wall clock
A flying bird
A swing in motion

Translatory	Rotatory	Oscillatory	Repetitive	Random
Motion of a boy sitting on a merry-go-round	Revolution of the earth around the sun	Motion of your hands while running	Motion of a boy sitting on a merry-go-round	Motion of your hands while running
Motion of a train on a straight track		Swinging pendulum of a wall clock	Movement of the lungs during breathing	Motion of a train on a straight track
Revolution of the earth around the sun		A swing in motion	Revolution of the earth around the sun	Motion of a butterfly
Motion of a horse pulling a cart on a straight road			Swinging pendulum of a wall clock	A flying bird

UNIFORM & NON-UNIFORM MOTION

Uniform Motion: The motion in which the object moves a straight path covering equal distances in equal time intervals is called a uniform motion. For example – a car that moves 80 km in 1 hour again moves 80 km in the second hour.

Non-uniform Motion: The motion in which the object moves unequal distances in equal time intervals is called a non-uniform motion. For example – a car that moves 50 km in first hour, 30 km in second hour and 60 km in third hour.

DISTANCE & DISPLACEMENT

The change in the position of an object can be stated as displacement.

What is DISPLACEMENT?

The shortest possible distance travelled by an object from its initial to final position following a straight path is called displacement. For example: a cat that travels A to B position and eventually turns to C. In such a case, the cat ultimately travels length AC, which is its displacement (shortest possible distance).

Distance and displacement are both distinct terms. Displacement is the shortest possible distance of an object as you have seen above with the help of the diagram, whereas distance is the actual length covered by an object (AB + BC) {long distance}.

What is DISTANCE?

The distance of an object is defined as the actual length travelled by an object (see the above diagram’s KEY).

Differentiate between DISPLACEMENT and DISTANCE.

Displacement

1) It is the shortest possible distance.

2) It is crucial to mention the directions (e.g. you cannot write CA, you have to show the direction so write AC)

Distance

1) It is a long distance as compared to displacement.

2) It is NOT necessary to mention the directions as it is the aggregate length.

What SIMILARITY do you observe in displacement and distance?

Both displacement and distance are expressed as lengths; therefore their SI units are metre (m).

Physical Quantities and Measurement II

October 7, 2023October 7, 2023

Hello friends,

Welcome to the exciting world of “Physical Quantities and Measurement II” These ideas are like the foundations of science, helping us measure and understand things like length, time, weight, and temperature. They make it easier for us to grasp how the physical world works and allow us to measure things accurately in science. So, let’s explore together how they’re essential in uncovering the secrets of the universe.

Measuring Length

In simple words, length means the distance of a straight line travelling through two points. To express distance through different methods, we use length, breadth (width), depth and height. The SI unit of length is metre and we denote it by an ‘m’.

To avoid confusion in the length of a metre throughout the world, the standard metre is put between two marks on a platinum-iridium bar kept at 0 degree located at the International Bureau of Weights and Measures in Sevres near Paris in France.

Every country owns a duplicate of the original metre for correct measurements of metre ruler which they manufacture. In India, the standard metre is there at the National Physical Laboratory in Delhi.

Common devices used to measure length

Some of the common devices used to measure length are –

1. Ruler –

Used for small measure.
Generally, available in 15 cm (6 inches) or 30 cm (12 inches).
A centimetre is further divided into 10 millimetres.

2. Metre Rod –

Has a fixed length of a metre.
It has 100 divisions, each of 1 cm (1m = 100cm).
A centimetre has 10 millimetres.
Generally, used by cloth merchants (tailors).

3. Measuring Tape –

Can contain more than one metres.
Used to measure long lengths (length of a field).
Have a flexible movement to measure curved objects too (size of a person’s chest, circumference of a tree trunk).

How to use a ruler correctly?

Reading correct measurement using a ruler plays a very important role. So, in order to take the correct measurement from the ruler, you will have to follow these certain steps.

• Avoid using the ends of a ruler – If you use your ruler in an improper way or you use it regularly, the edges and corners of your ruler get broken and it does not give that perfect line design on your notebook. So to prevent this problem, you should not put the left edge of the object (to measured) straight at the zero mark.

• Placing the ruler correctly – For a very correct measurement of your object, you should keep the ruler exactly parallel to the object and keep it as near as possible.

• Correct positioning of eyes – Correct positioning of eyes while measurement matters a lot. Whenever you are doing measurement with a ruler, you should always keep your eyes vertically and horizontally straight in line with the mark you are reading. Parallax error is the error which can be made while reading the measurement using a ruler.

Indirect Measurement of Length by Using a Ruler

To measure a curved or designed line using a ruler, you can do the following steps and you will definitely get the correct measurement.

Fetch a piece of thread.
Put the thread along the whole line and cut it wherever it ends.
Take a ruler and put the thread parallel to its marking.
Measure the length of the thread using the ruler.
The measured value of the curved line will be displayed.

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Measuring Mass

The amount of matter (solid, liquid, gas) present in the object is mass. The SI Unit of mass is ‘Kilogram (Kg)’. Generally, we don’t use the word mass in our daily life. Instead, we use the word weight. Suppose, if you purchase 3 kg of potatoes from a vegetable vendor then actually you are purchasing 3 kg mass of the potatoes.

The very common submultiples of mass are gram (g) and milligram (mg). We use these submultiples of mass to measure smaller quantities whereas, and quintal and metric ton to measure very big quantities.

Devices Used to Measure Mass

People have developed several devices to measure mass till date. Beam Balance/Grocer’s Balance, Electronic Weighing Machine and Physical Balance are some of the common devices for the same. Let’s move into deep detailed version of these devices.

1. Beam Balance (tarazu)

This is the simplest type of instrument which we can use to measure mass. Let’s see the structure of the beam balance:

We take the standard weights as a fixed quantity and the compare the unknown quantity with it.
Beam balance has a straight metal beam which is generally of iron.
Iron rod is supported with an iron loop in the centre.
There is a pointer between the iron loop.
We hang two identical pans from the two ends of the rod equally.
Both the pans are equal in their length and mass so that we don’t get a wrong weight.
Object (whose mass has to be calculated) is generally put on the right pan.
After that, we put the standard weights on the left pan.
Then, we put these fixed units in an increasing way on the pan till the metallic beam turns horizontal and the pointer becomes vertical.
At last, we take out the sum of the standard weights and calculate the mass of the object.

*One thing in notice that, when both the pans are empty, the metallic beam should be horizontal and the pointer should be vertical.

2. Common type of beam balance

Nowadays in the shops, there is a different type of beam balance (somewhat type of a digital machine, but not exactly digital) which is similar to the normal one. There are some changes as given in the points below-

No beam is present but a pointer is there.
The pointer moves whether right side or the left side in a rainbow shape according to the weight put on it.
So, if we compare this version with the traditional beam balance then we can say that if the pointer becomes vertical in this digital version then it means that both the pans have equal mass.

3. Electronic Weighing Machine

An electronic weighing machine is also a good device for measurement of mass. In this device, the measurement of mass doesn’t need to have the standard weights. Instead, it uses the LCD display panel right on its top which displays the mass of the object digitally.

4. Physical Balance

In the science laboratories or in a jewellery shop, the accuracy plays a very very important role. We can’t do these types of measurements using devices like beam balance. So, for that reason, we have a physical balance. A physical balance can do very sensitive calculations of mass measurement.

Measuring Time (Physical Quantities & Measurement II)

Time is very important for every task we do in our day to day life. The SI Unit of time is ‘second (s)’. Some other very common units of time that we use daily in our life is – minute (min), hour (h) and mean solar day.

Mean solar day is the time that the earth takes to complete one whole rotation in its own axis.

To measure the time of the day we use some units like- hour, minute and second. Commonly, we use the 12-hour clock system in which the day contains two periods of 12-hours.

What is a.m. and p.m.? – a.m. is the time from the midnight to the noon (12:00 in extreme morning till 12:00 in afternoon) and p.m. is the period from noon to again midnight (12:00 in afternoon till 12:00 extreme morning/night).

Devices for time measurement

To measure time, we can use many devices, like – nowadays, use of analogue and digital clocks, (in the past, use of sundial and sand clocks). Let’s go in more detail of these devices.

1. Sundial

The ancient people did not had very good facilities, thus they measured time by the movements of sun, moon, stars and other heavenly bodies. Later on, the ancient Greeks had prepared a device which was the sundial. The sundial was having the intelligence which says that when the position of the rod placed on it changes means that time has also passed and accordingly they used to measure time.

2. Sand Clock

The second ancient device developed was the sand clock. The intelligence put in this device was when the sand in the upper chamber of the device falls in the lower chamber, a fixed amount of time has passed.

3. Analogue Clock

The third device which is a very common device for time measurement in the modern world. It’s the analogue clock. These clocks are in a circular shape (and sometimes other shapes) with numbers from 1-12 written on it in the circular manner. It has two hands or maybe three hands at times which can rotate from the centre point of the circular dial. The three hands have a specific size and thickness to indicate a specific time duration, like the second hand is the longest and thinnest which indicates the seconds. A little shorter and little thicker hand reads the minutes whereas the shortest and the thickest hand indicates the hours and accordingly we note down the time of the analogue clock. The 12-hour time has 60 minutes and the 60 minute scale has 60 seconds, if any.

4. Digital Clock

The fourth and the last device is the digital clock which as the name suggests, displays the time digitally in number format. It shows the time in either ‘hours and minutes’ or in ‘minutes, hours and seconds’.

Physical Quantities & Measurement | Physics | KnockLedge

Time Intervals

Now, we’ve talked a lot about time, let’s try to know about the time intervals. We use time intervals to measure the time of an event having a fixed duration. To get an appropriate duration of the event, we can start or stop the stop watches and stop clocks at the beginning and at the end of a task.

24-hour Clock System

In the 24-hour clock system, we use the number of hours that have passed since midnight. We do not repeat the numbers two times as in the analogue system. The time from 00:00 till 12:00 indicates the time duration from midnight to afternoon whereas, time from 12:00 till 24:00 (or 00:00) indicates time duration from afternoon to midnight.

E.g. – 02:30 hours means 2:30 a.m., 17:00 hours means 5:00 p.m.

(V.I.P Formula: 17:00 – 12:00 = 5:00).

Public facilities like railways and airlines have a non-stop 24-hour duty and thus they use the 24-hour clock system.

Main Features

The use of a.m. and p.m. in the timings is not there to avoid confusion.
We show the time by displaying 4 specific digits. The first two digits show the number of hours and the next two digits show the number of minutes.
We divide the hours and minutes by a colon (:) in 2 pairs of 2 digits.
Time continuously passes one number by number without any repetition.
The time 00:00 and 24:00 are both same.

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