Notes on Measurement: Length and Mass | Grade 7 > Science > Measurement | KULLABS.COM

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#### Introduction

All the substances around us can be measured by using various units like the mass of gold, length of clothes, the quantity of milk, etc. Those quantities which can be measured is known as physical quantities like length, mass, etc. To express the magnitude of a physical quantity, we compare that quantity with a known standard quantity of the same kind. The comparison of an unknown quantity with a known standard quantity of the same kind is called measurement. Measurement is very important in our daily life.

#### Importance

• It is essential for selling and buying goods.
• It is used in scientific experiments to establish the truth about a physical phenomenon.
• It is essential in performing the experiment for making our daily food.
• It is required in the global understanding of the quantity of a substance.

#### Systems of measurement

A system of measurement is a collection of units of measurement and rules relating them to each other. There are various systems of measurement which are given below

• CGS System: It stands for centimeter, gram and seconds. In this system, length is measured in centimeter, weight is measured in gram, and time is measured in seconds.

• MKS System: MKS stands for meter, kilogram and seconds. Here, length is measured in meter, weight in kilogram and time in seconds.

• FPS System: FPS stands for foot, pound, and seconds. Here, length is measured in the foot, weight in pound and time in seconds.

• SI System: This is the extension of MKS system. It stands for System de International.

#### SI Systems

Local system of measurement varies from place to place. So, to make the measurement system more scientific, convenient and uniform, the 12th General Conference of Weight and Measures adopted an international system of units which is known as SI units in October 1960. This system of measurement is used throughout the world. There are seven fundamental units of measurement in SI Systems, which are given in the table below:

 S.N. Physical quantities SI units 1. Length Metre (m) 2. Mass Kilogram (kg) 3. Time Second (s) 4. Temperature Kelvin (K) 5. Electric current Ampere (A) 6. Luminous intensity Candela (cd) 7. Amount of substances Mole (mol)

#### Length

It is the distance between any two points. Breadth, radius, height, diameter, thickness, etc. are forms of length. Length is measured by using the scale, meter rod, inch tape, measuring tape, etc. To measure the length, the given object is compared to the standard length of a scale, meter rod or a measuring tape. The scale is used to measure short distance and meter rod is used for measuring long distance. Meter is the standard unit of measurement.

Units of length

The SI unit of length is a meter(m). There are many other units of length like the millimeter, decimeter, etc. which are given below with their relation:

10 millimeter = 1centimeter
10 centimetre = 1 decimetre
10 decimetre = 1 decameter
10 decametre = 1 hectometre
10 hectometre = 1 kilometre

Among all units, millimeter, centimeter, meter, and kilometer are widely used.

1 centimetre = 10 millimetre
1 metre = 100 centimetre
1 kilometre = 100 metre

Measuring the Diameter of Spherical Objects

Diameter is the distance between two points of the spherical objects like the ball, cricket ball, orange, etc. To measure the diameter at first the spherical object is placed on top of the table or a plane surface. Then two solid blocks are placed at both sides of the spherical objects. The lower edges of the blocks are adjusted with the scale. The reading of the position of two faces,one of each block touching the spherical object is taken.

#### Mass

The amount of matter contained in a body is called mass. It's SI unit is kilogram (kg). Other similar units are also used for its measurement like milligram (mg), gram(g) quintal, metric ton, etc.

Measurement of Mass

For the measurement of the mass of a body, we use beam balance. It is made of a horizontal beam supported at its center and two similar pans suspended at equal distances from the center of the beam. It is used by shopkeepers, goldsmiths, scientists, etc. Shopkeepers use an ordinary grocer's beam balance whereas goldsmiths and scientist use a physical balance for accurate measurement.

About the measurement of mass in beam balance, at first, the object whose weight is to be measured should be placed on one of the pans of beam balance and standard objects should be kept in another pan until the pans are balanced and the beam is horizontal once again. After the pans become balanced, the weight of the object is calculated or given by the sum total of the standard weights used.
There are various units used for the measurement of mass like kilogram, gram, milligram, quintal, etc. Milligram and gram are used in the measurement of light objects whereas kilogram is used in the measurement of heavy objects. The mass of very heavy objects is measured in quintal and metric ton.

Units of Mass

1000 milligram= 1 gram
1000 gram= 1 kilogram
100 kilogram= 1 quintal
10 quintal= 1 metric ton

• The comparison of an unknown physical quantity with the known standard quantity of the same kind is called measurement.
• The quantities which can be measured are called physical quantities.
• The unit of temperature is kelvin.
• The unit of luminous intensity is candela.
• The distance between any two points is called length.
• The quantity of matter contained in a body is called its mass.
• The SI unit of mass is kilogram(kg).
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### Very Short Questions

• Measurement: The comparison of unknown physical quantity with the known standard quantity of the same kind is called measurement.
• Physical quantities: Physical quantities are those quantities that can be measured.

Names of any five physical quantities are length, mass, time, area and volume.

The SI unit of the given physical quantities is given below,

• Length: Metre
• Time: Seconds
• Temperature; Kelvin
• Electric current: Ampere
• Luminous intensity: Candela

The distance between any two points is called length.
Any three units of length are centimetre. inch and mile.

Any three importance of measurement is given below,

• It is essential in performing the experiment for making our daily food.
• It is required in the global understanding of the quantity of a substance.
• Measurement of medicine is a must in the treatment of diseases.

The quantity of matter contained in a body is called its mass. The SI unit of mass is a kilogram. Any three units of mass are gram, quintal, and metric ton.

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Volume
Pride
Area
Pressure

Metre
Minute
Seconds
Kilogram

Kelvin
Minute
Ampere
Candela

Second
Kilogram
Ampere
Metre

Mole
Second
Metre
Kilogram

Kilogram
Mole
Ampere
Candela

Volume
Mass
Mole
Area
• ### One kilogram is equal to

10000 milligram
100000 milligram
100 gram
1000000 milligram

Space
Length
Displacement
Area

Kilometre
Centigram
Gram
Kilogram

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