Chapter 10

Motion and Measurement of Distances

One of the most important things that scientists do is to perform experiments. Experiments are done by taking 'measurements'. Taking a measurement is assigning a numerical value to something that can be measured, such as length, mass, temperature, or volume. Determining the length, size, or amount of a measurable thing is known as measurement.

A physical quantity (such as length) must be measured against another physical quantity. A thing moving in relation to another is considered to be in motion. For example, when a car runs along the road, it moves in relation to the trees and poles, which are 'not moving.'
When the location of an object (with relation to another item) varies over time, it is said to be in motion.

 

STANDARD UNITS OF MEASUREMENTS in Motion And Measurement Of Distances Class 6

The people of the Indus Valley Civilisation were quite good at measuring lengths. They used diverse body parts to measure the length, such as the hand span, cubit, and fathom. The distance between the elbow and the tip of the middle finger is measured in cubits (outstretched). Other length units based on bodily parts include the foot, yard, and pace. However, they are unreliable since body component length varies from person to person. As a result, the necessity for conventional units of measurement became apparent.
Standard units of measurement are units with a defined amount that do not change from person to person or place to place. The metric system, for example, was developed by the French in 1790 and is a set of standard units.

On the other hand, adopting a standard method of measuring did not address the problem. People in various nations were still utilising separate sets of standard units for measuring in such a setting. As a result, scientists worldwide created a single set of units known as the International System of Units to ensure worldwide consistency (also known as SI Units). The SI Units was implemented in 1960, and it has made communication between scientists from various nations much simpler since then.
The SI Unit of length is the metre. Other frequent length units are the millimetre (mm), centimetre (cm), and kilometre (km).

One kilometre (km) is split into 1000 equal parts, each referred to as a metre (m). One metre is split into 100 equal divisions, each referred to as a centimetre (cm), which is further subdivided into ten equal divisions, each referred to as a millimetre (mm).
Thus, 1 km = 1000 m, 1 m = 100 cm and 1 cm = 10 mm.

The term "length" refers to the distance between two points.
A ruler, a measuring tape, a metre rod, and other tools can be used to determine length, depending on what is most suitable for the task at hand.

While measuring length using a ruler, we should take the following precautions:

  1. It's important to keep the ruler parallel to the object's length.
  2. If the ruler's edge is worn out or damaged, the measurement should begin at any other completely visible mark. The length is 3 cm (6 cm – 3 cm = 3cm) if you measure from the 3 cm mark to the 6 cm mark.
  3. Your eyes should be immediately above the spot where the measurement is. This is to avoid mistakes when conducting observations and thereby to record measurements. You may receive incorrect readings if they are in different places.

A metre scale cannot be used to measure the length of a curving line directly. To measure the length of a curved line, we use a string. Put a knot on one of the string ends, for example, if you need to measure the length of a curved line AB. The knot should be tied on point A. Hold the string taut with your fingers and thumb, then insert a tiny section of the string down the line while holding it taut. Fix your hand's location, and therefore the knot on the string, at endpoint A, and then move the other hand along the curving line.

Make sure the string encircles the whole curved line. Repeat the process until you reach endpoint B, which is the other end of the curved line. Mark the thread at Point B and extend it along a metre scale. The curved line is the length of the thread between the knot and the designated spot.

There are many different types of motion: rectilinear, circular periodic, and non-periodic.

Rectilinear Motion

Rectilinear motion is a form of motion in which things move in a straight path.
Some instances of rectilinear motion are the falling of a stone, automobiles driving on a straight road, and sprinters running on a straight track.

Circular Motion

Circular motion is defined as the movement of an item along a circular route with a fixed centre. If you attach a string to a stone and then twirl it with your hand, you'll observe that it moves in the same round direction while maintaining the same distance between the stone and your hand.

Periodic Motion

Periodic motion is a type of motion that repeats at regular/equal periods of time. The to and fro motion of a pendulum, the hands of a clock, the movement of a swing, and the plucked string of a guitar are all examples of periodic motion.

Non-Periodic Motion

Non-periodic motion is defined as motion that does not repeat itself at regular intervals of time or does not repeat itself at all. A bird gliding over the sky, a car going along the road, and children playing in a park are all examples of non-periodic motion.

Important NCERT Answers

Give two instances of land, sea, and air forms of transportation.
Answers –
Modes of transport used on land: Car, Truck
Modes of transport used in water: Ship, Submarine
Modes of transport used in the air: Aeroplane, Helicopter

Fill in the blanks:

(i)  A metre is equal to ____________ cm.

(ii) The length of five kilometres is __________ metres.

(iii) On a swing, a child's motion is __________ .

(iv) The motion of a sewing machine needle is ________.

(v) The motion of a bicycle's wheel is______________.

Answers –

(i) 100

(ii) 5000

(iii) Periodic

(iv) Periodic

(v) Circular

Why can't a pace or a footstep be used as a measurement unit?
Answer – A pace or a footstep cannot be used as a standard unit of length because it varies from person to person. The length measured by one’s footsteps may not be the same as some other person’s.

Arrange the following lengths in ascending order: 1 metre, 1 centimetre, 1 kilometre, 1 millimetre.

Answer – 1 millimetre, 1 centimetre, 1 metre, 1 kilometre

A person's height is 1.65 metres. It should be expressed in centimetres and millimetres.

Answer – 1.65 m = 165 cm = 1650 mm

Radha's house and her school are 3250 metres apart. Calculate the distance in kilometres.

Answer – 1 km = 1000 m

Therefore, 1 m = 1/1000 km

Thus, 3250 m = 3.25 km

So, the distance between Radha's home and her school is 3.25 km.

The scale reads 3.0 cm at one end and 33.1 cm at the other end when measuring the length of a knitting needle. I'm curious about the needle's length.

Answer – Length of needle = 33.1 cm – 3.0 cm = 30.1 cm

Write out the similarities and differences between the motion of a bicycle and that of a switched-on ceiling fan.

Answer – The motion of a bicycle and a switched-on ceiling fan is similar because the wheels of the bicycle and blades of the fan move around along a circular path around a fixed point. Thus, both the bicycle wheels and ceiling fans possess circular motion.
As the bicycle moves forward, it also comes under the category of rectilinear motion, but because the ceiling fan doesn't, it possesses only circular motion.

Why couldn't you measure distance using an elastic measuring tape? What challenges may you encounter if you tried to inform someone about a distance you measured with an elastic tape?

Answer – Being stretchable, the length of an elastic measuring tape would vary every time we would use it to measure a certain distance. We would obtain incorrect values of measurement because when multiple measurements are made, we'll obtain a different value each time we measure the same span of distance.

Two examples of periodic motion are shown.

Answer – Examples of periodic motion include the to and fro motion of a pendulum and the movement of a swing.

The process of determining the length, size, or amount of something is known as measurement. People in ancient times utilised non-standard length measures such as the hand span, cubit, and fathom. We now utilise the International System of Units (SI Unit), which is universally recognised and used. A metre is the SI unit for length (m).
A body is considered to be in motion when it moves with respect to another body. Rectilinear motion is defined as motion in a straight line, whereas circular motion is defined as motion on a circular route. An example of periodic motion includes the to and fro motion of a pendulum and the movement of a swing.

Learn more about the subject and related topics with MSVGo. MSVGo is a super-affordable online learning app that can make understanding math and science concepts easily and quickly. With 15,000+ videos, 10,000+ questions bank, and video solutions to textbook questions, the MSVGo can become your study buddy. Get the app for free and become an MSVGo Champ today!

Other Courses

Related Chapters