Motion and Measurement of Distances Class 6 Notes

Motion is the change in position of an object with respect to time. The movement of a body or an object from one place to another is known as motion. Different objects show varying types of motion. Motion can be classified into three types namely Rectilinear Motion, Circular Motion, and Periodic Motion. The path covered during the motion is known as distance. 

The object used to move from one place to another is known as the means of transport. The modes of transport we see or use today have a long history of evolution and milestones. The means of transport used by us today are a result of many milestones. The various means of transport are Roadways, Railways, Waterways, and Airways. Measurement is another aspect that has changed over the years. The system used today for measurement is referred to as The International System of Units (SI Units).

Read More: NCERT Solutions for Class 6 Science Motion and Measurement of Distances

Key Terms: Motion, Distance, SI Unit, Rectilinear Motion, Measurement, Unit of Measurement, Circular Motion, Time, Periodic Motion

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What is Motion?

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Motion is the movement of an object or a thing or a force that leads or causes that motion. Motion can be defined as the change of the place or location of an object or thing with time. Anything that changes its position with time is known to be in motion. A man walking, water flowing in the river, a pencil falling from the table, etc are all examples of motion.

Motion 

The study of motion is important in one’s day-to-day life and, some terms that help describe motion are

1. Distance
2. Speed
3. Time
4. Displacement

Also Read:

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Types of Motion

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All the objects or bodies do not move in the same way. Every object has its way of moving, like bicycle tires moving round and round, but the bicycle moves straight along the road, and the pendulum of a clock moves clockwise.

There are three types of motion:

1. Rectilinear Motion
2. Circular Motion
3. Periodic Motion

Rectilinear Motion

• When an object or body moves along a straight line in a given time, it is defined as rectilinear motion.
• Example: A car moving on a road, fruit falling from a tree, a pencil rolling on the table.

Circular Motion

• When an object or body moves in a circular path, it is known as circular motion but may or may not change the distance to time.
• Example: Movement of a blade of the fan, the motion of the spinning top.

Read More: Uniform Circular Motion

Periodic Motion

• A motion that leads to repletion within an interval of time is known as periodic motion. It can also be defined as if the object moves to and fro is known as periodic motion.
• Example: Pendulum of the clock, motion of a swing.

Read More: Oscillations

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Distance

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Distance is defined as the path which is being covered while moving from one place to another. It is the measure of the path which is being covered or how far or long the object or thing is. The length of the cloth, the path covered from Delhi to Chandigarh, the length of the stadium, etc, are all examples of distance.

Displacement is the shortest distance between two places. It is also defined as the change in the position of the object. Displacement can be zero, but distance cannot be zero if there is motion.

Read More: Unit of Displacement

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Means of Transport

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In earlier times, people used to travel from one place to another by walking because there was no means of transport. With the evolution of humans, there were various ways and means and different routes for transport like water and roads.

• With the invention of the wheel, the mode of transportation became easier.
• Since ancient times people have been using different means of transport for traveling from one place to another.
• Different types of boats are used for traveling in water bodies. Animal-driven carts, vehicles, and automobiles are used for traveling in rods.

The various mode of transport are as follows:

Road Ways 

• The first means of transport that were used by man were carts and carriages. 
• Cars and buses came into existence much later. 
• The first car with internal combustion was invented in 1906, which is now the basis of many trains and cars. 

Railways 

• Trains as a means of transport are just 500 years old.
• Iron was used in railways in the 18th century. 
• Steam run trains were used as means of long-distance traveling after the invention of steam engines in 1820.
• Electric trains and monorails knocked on the doors of rail transportation in the 19th century. 
• Super fast Bullet train is the most modern form of traveling long distances. 

Waterways 

• Initially wooden logs were used as ways of crossing rivers and lakes. 
• The wooden logs were cut into plates to form boats in later years. 
• Boats are still the easiest way of transportation across lakes and ponds. 
• The larger means of transport in the water like ships and motorboats replaced boats with the invention of motors and engines. 

Airways 

• Hot air balloons and gliders were used as means of air transport. 
• In 1903, humans actually flew whose credit goes to the famous Wright brothers. 
• Until the 21st century, airways were used only for military purposes. 
• The modern airplanes and helicopters came into existence for various human transportation uses in the 21st century only. 

Read More: History of Transportation

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Measurement 

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Various traditional methods were used to measure distance and length. In ancient times, people used a length of a foot, the width of a finger, and distances of footsteps to measure distance and also as different units of measurement.

• The people who sell flowers use their forearms as a unit of measurement for making garlands even today and it is an example of measurement of length of the garland.
• Every person has different sizes of body parts so there was confusion in measurement which was the reason the metric system was introduced.
• The changing sizes with changing bodies hindered the accuracy of these measurements. 
• Thus, a standard form of measurement was eventually discovered, which is universally used and accepted today.

Units of Measuring Length in Olden Days

Read More: Uncertainty in Measurement

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Standard Unit of Measurement

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To break the confusion of measurement, the French introduced a common standard unit of measurement, which is used all over the world.

• The standard unit of measurement is called the international systems of unit ( S.I. Unit). The S.I. Unit of length is a meter.
• Each meter (m) is divided into 100 centimeters (cm) which is a C.G.S unit.
• For measuring distances that are very large kilometers are used that is, 1 km = 1000 meters.
• The various units for measuring length are cm, m, km, mm, etc.

These metric units are related in the following ways: 

1cm = 10 mm 

1m = 100 cm 

1km= 1000 m

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Zero Error and Correct Way to Measure Length

The correct way to measure the length is:

• Place the scale in contact with the object or thing, which is to be measured.
• The position of the eye should be correct to take proper measurements and avoid parallax errors.
• The zero mark on the scale should be properly visible. If the zero mark is not visible, the measurement from that scale should be avoided.
• The scale should be properly placed to measure correctly.

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Errors in Measurement

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There can be various times when the measurement goes wrong because of various reasons like the wrong placement of the scale, or wrong eye position which leads to parallax error.

Parallax Error

Parallax is the change in the original position of the object or thing when it is viewed from a different point or a different position. If such an error occurs while measuring is known as a parallax error.

Parallax Error

Read More: Measurement of Mass and Weight

How to Measure a Curved Line?

We cannot use meter scales to measure curved lines. So, We use thread to measure the length of curved lines.

• A knot is created at one end, and it is used as a starting point to measure the curved path or line.
• Stretch the thread till the whole curved path is covered, and then mark it on the thread.
• Measure the length from the beginning and the final mark on the thread with the help of a meter scale.

Time

Time is defined as the unit which is used to measure the distance it covers in that period. Distance is measured, with respect to time.

D = S x T

Where

• D = Distance covered.
• t = Time taken to cover the distance.
• s = Speed in which the object or body is moving.

Read More: Unit of Time

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Things to Remember

• The movement of any object with respect to time is known as motion.
• The path covered by an object is known as distance.
• Motion in a straight line is called rectilinear motion, while motion in circular paths is known as circular motion.
• Different means of transport are used to travel from one place to another.
• In earlier times, people used to measure through their feet, fingers, forearms, etc. which lead to confusion.
• The SI unit of measurement was introduced by the French to break the confusion all over the world and is used today worldwide.