The unit is known as definite magnitude of a physical quantity . The physical quantities can be measured by using various units depends upon the quantities. For example the weight of the rice, sugar etc can be calculated by using kilogram, gram, tons etc.

A system of weights and measures based on the principle that each and every quantity should have one unit whose multiples and sub multiples are all derived by multiplying or dividing by powers of ten. The standard unit is also called as **metric system**. In this section we will learn more about different units and its conversions.

In Volume we normally use liter to represent as the standard unit, and the other standard units are

1 milliliter = $0.001$ liter

1 centiliter = $0.01$ liter

1 deciliter = $0.1$ liter

1 decaliter = $10$ liters

1 hectoliter = $100$ liters

1 kiloliter = $1000$ liters

1 cubic inch = $1.639 \times 10^{-2}$ liters

1 gallon = $3.785$ liters

1 cubic foot = $28.316$ liters

In length, we normally use meter to represent as the standard unit, which is abbreviated as $m$. The other standard units are

1 millimeter = $0.001$ meter

1 centimeter = $0.01$ meter

1 decimeter = $0.1$ meter

1 decameter = $10$ meters

1 hectometer = $100$ meters

1 kilometer = $1000$ meters

1 inch = $2.54 \times 10^{-2}$ meters

1 foot = $0.3048$ meters

1 angstrom = $1 \times 10^{-10}$ meters

1 fermi = $1 \times 10^{-15}$ meters

1 light year = $0.946 \times 10^{16}$ meters

1 mile = $1.609344$ km

1 mile = $1.609344$ km

In Mass, we normally use gram to represent as the standard unit, and the other standard units are

1 milligram = $0.001$ gram

1 centigram = $0.01$ gram

1 decigram = $0.1$ gram

1 decagram = $10$ grams

1 hectogram = $100$ grams

1 kilogram = $1000$ grams

1 stone = $6350.29$ grams

1 pound = $453.592$ grams

1 ounce = $28.3495$ grams

The standard units in time are

1 minute = $60$ seconds

1 hour = $60$ minutes = $3600$ seconds

1 day = $24$ hours

1 week = $7$ days

1 year = $365 \frac{1}{4}$ days (for the Earth to travel once around the sun)

The basic units in which the energy measured is joule (J). The other units of energy are given below

1 BTU (British thermal unit) = $1055$ Joule

1 erg = $1 \times 10^{-7}$ Joule

1 foot pound = $1.356$ Joule

1 calorie = $4.186$ Joule

1 kilowatt hour = $3.6 \times 10^{6}$ Joule

1 electron volt = $1.602 \times 10^{-19}$ Joule

1 liter atmosphere = $101.13$ Joule

The basic units in which the area measured is square meter ($m^{2}$). The other units of area are given below

1 sq. inch = $6.4516 \times 10^{-4}$ square meter

1 sq. Foot = $9.2903 \times 10^{-2}$ square meter

1 acre = $4.0468 \times 10^{3}$ square meter

1 hectare = $1 \times 10^{4}$ square meter

1 sq. mile = $2.5888 \times 10^{6}$ square meter

1 barn = $1 \times 10^{-28}$ square meter

The basic units in which the area measured is watt ($W$). The other units of pressure are given below

1 erg/sec = $1 \times 10^{-5}$ watt

1 BTU/hr = $0.2930$ watt

1 foot pound/sec = $1.356$ watt

1 horsepower = $745.7$ watt

1 calorie/sec = $4.186$ watt

The basic units in which the force measured is Newton ($N$). The other units of force are given below

1 dyne = $1 \times 10^{-5}$ Newton

1 pound = $4.448$ Newton

The basic units in which the density measured is kilogram/cube meter (kg/$m^{3}$). The other units of density are given below

1 slug/cu ft = $515.4$ kilogram/cube meter

1 pound / cu in = $2.768 \times 10^{4}$ kilogram/cube meter

In viscosity we normally use kg/m.s to represent as the standard unit, and the other standard units are

1 poise = $0.1$ kg/m.s

1 slug/ft . S = $4.79 \times 10^{1}$ kg/m.s

The following are the unit conversion problems.

Given, girl travels 4 miles and 3 km.

We know that,

1 mile = $1.609344$ km

4 miles = $4 \times 1.609344$ km

= $6.437376$ km

Total travel distance = $6.437376$ km + $3$ km

= $9.437376$ km

We know that 1 km = $1000$ m

$9.437376$ km = $9.437376 \times 1000$ m

= $9437.376$ km

We knew that $1$ kg = $1000$ grams

We need to find $5$ kilogram into grams.

Multiply $5$ with $1000$ = $5000$ grams.

Therefore, $5$ kilograms = $5000$ grams

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