The Story of Transport

The history of transport is a fascinating story of human innovation, detailing how we conquered distance over time. From simple foot travel to complex spacecraft, the means of transport have evolved dramatically, shaping civilizations and connecting the world.

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Ancient Modes of Transport

In ancient times, people had no sophisticated means of transport. They relied on the most basic methods:

• On Foot: The earliest form of travel was simply walking. People would carry goods on their backs.
• Use of Animals: Later, humans began to domesticate animals like bullocks, horses, and camels for transportation, which allowed them to travel farther and carry heavier loads.
• Early Boats: For transport through water, early humans used simple boats. Initially, these were just logs of wood with a hollow cavity. Over time, people learned to assemble pieces of wood to create more complex boats, often imitating the shapes of aquatic animals. This streamlined shape, similar to that of a fish, helped the boats move efficiently through water.

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The Revolution of the Wheel and Engine

Two major inventions completely transformed the modes of transport.

1. Invention of the Wheel:

The invention of the wheel was a monumental leap. Over thousands of years, the design of the wheel was improved, and animals were used to pull carts that moved on wheels, making land transport much easier and more efficient.

2. Invention of the Steam Engine:

Until the beginning of the 19th century, people still depended heavily on animal power. The invention of the steam engine in the 19th century led to the development of new, powerful means of transport. This included steam engine-driven carriages and wagons that ran on railroads.

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Modern Means of Transport

Following the steam engine, the pace of innovation accelerated, especially in the 20th century.

• Automobiles: The late 19th and early 20th centuries saw the development of automobiles like motor cars, trucks, and buses.
• Motorised Ships: Motorised boats and ships replaced wind-powered vessels for water transport.
• Aeroplanes: The early years of the 1900s saw the development of aeroplanes, which were later improved to carry passengers and goods across vast distances in a short time.
• 20th Century Contributions: The 20th century brought even more advanced modes like electric trains, monorails, supersonic aeroplanes, and spacecraft.

The Need for Measurement

It is often important to know how far a place is or how long an object is. This knowledge, called measurement, helps us make decisions in our daily lives. For example, we need to know the distance to school to decide whether to walk or take a bus. A tailor needs to measure cloth, and a carpenter needs to measure wood.

Measurement is essentially the comparison of an unknown quantity with a known, fixed quantity. This known, fixed quantity is called a unit. The result of a measurement is always expressed in two parts: a number and a unit (e.g., 12 foot lengths).

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The Problem with Non-Standard Units

Before the development of standard scales, people used various non-standard units for measurement. The story of Paheli and Boojho illustrates the problem with such methods.

The Gilli Danda Measurement Story

Paheli and Boojho decided to measure their shared desk to divide it equally. They used a set of gilli and danda for this.

• First Measurement: They found the desk's length to be two danda lengths and two gilli lengths. They happily drew a line in the middle, giving each a share of one danda and one gilli.
• The Problem: After a few days, the line was wiped out. Boojho lost his old set and brought a new gilli and danda. When they measured the desk again, the length was different: two danda lengths, one gilli length, and a small portion left over.

This created a problem because the length of the gilli and danda in the new set was different from the old one. This highlights the core issue with non-standard units: they are not consistent and can vary from person to person or from one object to another.

Similarly, using body parts like a foot or a handspan for measurement leads to confusion because the size of these body parts is different for different people. If one person measures a room as 12 foot lengths and another measures it as 14 foot lengths, it is impossible to know the actual size without a common reference.

This confusion created the need for standard units of measurement that do not change from person to person and are uniform everywhere.

Standard Units of Measurement

To overcome the confusion caused by non-standard units, a uniform system of measurement was developed.

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Historical Non-Standard Units

Throughout history, people used parts of the body for measurement. These units were convenient but inconsistent.

• Cubit: The length from the elbow to the fingertips, used in ancient Egypt.
• Foot: The length of a foot, used in many parts of the world.
• Yard: The distance from the chin to the tip of the outstretched arm.
• Pace or Step: Used by the Romans for measuring distance.
• Angul (finger) or Mutthi (fist): Small length measurements used in ancient India.

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The Metric System and SI Units

In 1790, for the sake of uniformity, the French created a standard unit of measurement called the metric system. This system was eventually adopted and refined by scientists worldwide.

The system of units now used globally is known as the International System of Units (SI units). Using SI units ensures that a measurement of a certain length, say one metre, means the same thing in India, France, or any other country.

SI Unit of Length

The SI unit of length is the metre (m).

For convenience, the metre is divided into smaller units or multiplied to form larger units.

• Each metre is divided into 100 equal divisions called centimetres (cm).
• Each centimetre is divided into 10 equal divisions called millimetres (mm).
• For measuring large distances, a larger unit called the kilometre (km) is used.

The standard conversions are:

$ 1 \text{ metre (m)} = 100 \text{ centimetres (cm)} $

$ 1 \text{ centimetre (cm)} = 10 \text{ millimetres (mm)} $

$ 1 \text{ kilometre (km)} = 1000 \text{ metres (m)} $

Correct Measurement of Length and Curved Lines

Using a standard unit is only the first step. To get an accurate measurement, we must also use the measuring device correctly.

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Precautions for Correct Measurement of Length

When using a scale to measure length, we need to take care of the following:

1. Placement of the Scale: The scale should be placed in contact with the object, exactly along the length that is being measured.
2. Reading from a Broken Scale: If the zero mark of a scale is unclear or its end is broken, you should not start the measurement from the zero mark. Instead, start from another full mark (e.g., 1.0 cm). Then, you must subtract this starting reading from the final reading to get the correct length.

   Example: If the starting reading is 1.0 cm and the final reading is 14.3 cm, the length is $ (14.3 - 1.0) \text{ cm} = 13.3 \text{ cm} $.

3. Correct Eye Position: Your eye must be positioned exactly vertically above the mark where the measurement is being taken. Looking at the mark from the side (from position 'A' or 'C') can cause an error in reading, known as parallax error. The correct position is 'B'.

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Measuring the Length of a Curved Line

We cannot measure the length of a curved line directly with a straight metre scale. For this, we can use a thread.

The Thread Method

1. Tie a knot at one end of the thread.
2. Place the knot at the starting point (A) of the curved line.
3. Carefully place the thread along the curved line, keeping it taut. Use your thumb and fingers to hold it in place as you move along the curve.
4. Continue until you reach the end point (B) of the line. Make a mark on the thread at this point.
5. Now, stretch the thread out straight along a metre scale.
6. Measure the length between the starting knot and the final mark on the thread. This length gives the length of the curved line.

Motion and its Types

In our surroundings, we see some objects that are stationary and others that are moving. This observation helps us understand the concepts of rest and motion.

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Rest and Motion

An object is said to be in motion if its position changes with time. For example, a flying bird or a moving train. An object is said to be at rest if its position does not change with time. For example, a house or a table.

Sometimes, an object at rest can have parts that are in motion. For example, a wall clock is at rest, but its hands are in motion. An electric fan is at rest, but its blades are in motion.

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Types of Motion

Motion can be classified into different types based on the path taken by the object.

1. Rectilinear Motion

When an object moves along a straight line, its motion is called rectilinear motion.

Examples: The motion of a vehicle on a straight road, the march-past of soldiers in a parade, a sprinter in a 100-metre race, a stone falling from a height.

2. Circular Motion

When an object moves along a circular path, its motion is called circular motion. In this motion, the distance of the object from a fixed central point remains the same.

Examples: The motion of a point marked on the blade of a rotating fan, the motion of the hands of a clock, a stone tied to a thread and whirled around.

3. Periodic Motion

When an object or a part of it repeats its motion after a fixed interval of time, its motion is called periodic motion.

Examples: The motion of a pendulum, a child on a swing, the strings of a guitar when plucked, the membrane of a tabla being played, the up-and-down movement of a sewing machine needle.

Combination of Motions

An object can often exhibit more than one type of motion at the same time.

Example: A ball rolling on the ground. The ball is moving forward along the ground, which is rectilinear motion. At the same time, it is also rotating about its axis, which is rotational motion (a type of circular motion).

Understanding these different types of motion helps us describe the complex movements we see everywhere around us.

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