Units and Measurement

<–2/”>a >Measurement of any physical quantity involves comparison with a certain basic, arbitrarily chosen, internationally accepted reference standard called unit. The result of a measurement of a physical quantity is expressed by a number (or numerical measure) accompanied by a unit.

A unit of measurement is a definite magnitude of a quantity, defined and adopted by convention or by law, that is used as a standard for measurement of the same quantity. Any other value of that quantity can be expressed as a simple multiple of the unit of measurement. For example, length is a physical quantity.

Four different systems of units are commonly used in science and engineering. The difference among them arises from the difference in the units used to represent the three fundamental quantities, namely length (l), mass (m) and time (t).

The base units for length, mass and time in these systems were as follows :

• In CGS system they were centimetre, gram and second respectively.

• In FPS system they were foot, pound and second respectively.

• In MKS system they were metre, kilogram and second respectively

Table of Contents

SI UNITS

SI Base Units

Base quantity	Name	Symbol
length	meter	m
mass	kilogram	kg
time	second	s
electric current	ampere	A
thermodynamic temperature	kelvin	K
amount of substance	mole	mol
luminous intensity	candela	cd

SI Derived Units:-

area	square meter	m²
volume	cubic meter	m³
speed, velocity	meter per second	m/s
acceleration	meter per second squared	m/s²
wave number	reciprocal meter	m^-1
mass density	kilogram per cubic meter	kg/m³
specific volume	cubic meter per kilogram	m³/kg
current density	ampere per square meter	A/m²
Magnetic Field strength	ampere per meter	A/m
amount-of-substance concentration	mole per cubic meter	mol/m³
luminance	candela per square meter	cd/m²

MKS SYSTEM

MKS unit of measurement is meter-kilogram-second. SI unit was derived from MKS system. In MKS system length is in meter (m), area is in square meter (m2 ), volume is in cubic meter (m3 ), time in second (s), mass is in kilogram (kg), weight (force) is in kilogram-meter per second square (kg-m/s2 ), density is in kilogram per centimeter square (kg/cm2 ), acceleration is in kilogram-meter per second square (kgm/s2 ), force(pressure) is in kilogram-force per square centimeter (kgf/cm2 ).

CGS SYSTEM

The CGS system was introduced formally by the British Association for the Advancement of Science in 1874. It found almost immediate favor with working scientists, and it was the system most commonly used in scientific work for many years. Meanwhile, the further development of the metric system was based on meter and kilogram standards created and distributed in 1889 by the International Bureau of Weights and Measures (BIPM). During the 20th century, metric units based on the meter and kilogram–the MKS units–were used more and more in commercial transactions, engineering, and other practical areas.

Units and Measurement

Units and measurement are the backbone of science and engineering. Without them, it would be impossible to communicate about the physical world or to make predictions about how it will behave.

There are many different systems of units, but the most widely used is the International System of Units (SI). SI is based on seven base units: the second, metre, kilogram, ampere, kelvin, mole, and candela. All other units in SI are derived from these seven base units.

The metric system is a decimal system of measurement that is based on the metre, kilogram, and second. It is the most widely used system of measurement in the world, and it is the official system of measurement in most countries.

The U.S. customary system is a system of measurement that is used in the United States. It is based on the foot, pound, and second. The U.S. customary system is not as widely used as the metric system, but it is still the official system of measurement in the United States.

The British imperial system is a system of measurement that is used in the United Kingdom and some other countries. It is based on the foot, pound, and second. The British imperial system is not as widely used as the metric system, but it is still the official system of measurement in some countries.

There are many other systems of measurement, but these are the three most common. Each system of measurement has its own advantages and disadvantages. The SI system is the most logical and consistent system, but it is not always the most convenient. The metric system is the most convenient system for everyday use, but it is not as precise as the SI system. The U.S. customary system is the most familiar system for people who live in the United States, but it is not as widely used as the metric system.

Units of measurement are used to quantify physical quantities. A physical quantity is a property of an object or system that can be measured. Examples of physical quantities include length, mass, time, temperature, and speed.

There are many different units of measurement for each physical quantity. The most common units of measurement are the SI units. SI units are based on the seven base units of the SI system. For example, the SI unit of length is the metre.

Other systems of measurement also use different units for each physical quantity. For example, the U.S. customary system uses the foot as the unit of length.

The choice of units of measurement depends on the application. For example, scientists and engineers typically use SI units, while people in everyday life typically use the units of the system of measurement that is most familiar to them.

Units of measurement are essential for Communication about the physical world. They allow us to quantify physical quantities and to compare them. Without units of measurement, it would be difficult to understand the physical world or to make predictions about how it will behave.

What is the difference between a hypothesis and a theory?

A hypothesis is a tentative statement about the relationship between two or more variables. A theory is a well-substantiated explanation of some aspect of the natural world, based on a body of facts that have been repeatedly confirmed through observation and experiment.

What is the difference between a fact and an opinion?

A fact is a statement that can be proven to be true. An opinion is a belief or judgment that is not necessarily true or false.

What is the difference between a cause and an effect?

A cause is an event or action that brings about a result. An effect is the result of a cause.

What is the difference between correlation and causation?

Correlation is a relationship between two variables that shows that they tend to vary together. Causation is a relationship between two variables in which one variable causes the other to change.

What is the difference between a dependent and an independent variable?

In an experiment, the independent variable is the one that is changed by the experimenter. The dependent variable is the one that is observed to see how it changes in response to the changes in the independent variable.

What is the difference between a control group and an experimental group?

In an experiment, the control group is the group that does not receive the treatment being tested. The experimental group is the group that receives the treatment being tested.

What is the difference between a random sample and a biased sample?

A random sample is a sample of individuals from a Population that is selected in such a way that every individual in the population has an equal chance of being selected. A biased sample is a sample of individuals from a population that is not selected in such a way that every individual in the population has an equal chance of being selected.

What is the difference between a descriptive statistic and an inferential statistic?

A descriptive statistic is a statistic that describes a sample. An inferential statistic is a statistic that is used to make inferences about a population based on the sample.

What is the difference between a mean, Median, and mode?

The mean is the Average of a set of numbers. The median is the middle number in a set of numbers when the numbers are arranged in order from least to greatest. The mode is the most common number in a set of numbers.

What is the difference between a normal distribution and a skewed distribution?

A normal distribution is a distribution of data that is bell-shaped. A skewed distribution is a distribution of data that is not bell-shaped.

What is the difference between a p-value and a confidence interval?

A p-value is the Probability of obtaining a result at least as extreme as the one observed if the null hypothesis were true. A confidence interval is a range of values that is likely to contain the true value of a population parameter.

What is the difference between a hypothesis test and a confidence interval?

A hypothesis test is a statistical test that is used to determine whether or not the null hypothesis is true. A confidence interval is a range of values that is likely to contain the true value of a population parameter.

What is the difference between a type I error and a type II error?

A type I error is the error of rejecting the null hypothesis when it is true. A type II error is the error of failing to reject the null hypothesis when it is false.

What is the difference between a power analysis and a sample size calculation?

A power analysis is a statistical procedure that is used to determine the sample size that is needed to achieve a desired level of power in a hypothesis test. A sample size calculation is a statistical procedure that is used to determine the sample size that is needed to estimate a population parameter with a desired level of precision.

Sure, here are some MCQs without mentioning the topic Units and Measurement:

What is the SI unit of mass?
(A) Kilogram
(B) Gram
(C) Newton
(D) Meter
What is the SI unit of time?
(A) Second
(B) Minute
(C) Hour
(D) Day
What is the SI unit of length?
(A) Meter
(B) Kilometer
(C) Centimeter
(D) Millimeter
What is the SI unit of speed?
(A) Meter per second
(B) Kilometer per hour
(C) Centimeter per second
(D) Millimeter per second
What is the SI unit of acceleration?
(A) Meter per second squared
(B) Kilometer per hour squared
(C) Centimeter per second squared
(D) Millimeter per second squared
What is the SI unit of force?
(A) Newton
(B) Kilogram-force
(C) Dyne
(D) Pound-force
What is the SI unit of pressure?
(A) Pascal
(B) Bar
(C) Atmosphere
(D) Torr
What is the SI unit of energy?
(A) Joule
(B) Calorie
(C) Watt-hour
(D) Kilowatt-hour
What is the SI unit of power?
(A) Watt
(B) Horsepower
(C) Kilowatt
(D) Megawatt
What is the SI unit of temperature?
(A) Kelvin
(B) Celsius
(C) Fahrenheit
(D) Rankine
What is the SI unit of amount of substance?
(A) Mole
(B) Kilogram
(C) Gram
(D) Mole
What is the SI unit of luminous intensity?
(A) Candela
(B) Lux
(C) Lumen
(D) Foot-candle
What is the SI unit of electric current?
(A) Ampere
(B) Coulomb
(C) Volt
(D) Ohm
What is the SI unit of electric potential difference?
(A) Volt
(B) Ampere
(C) Coulomb
(D) Ohm
What is the SI unit of electric resistance?
(A) Ohm
(B) Volt
(C) Ampere
(D) Coulomb
What is the SI unit of capacitance?
(A) Farad
(B) Henry
(C) Tesla
(D) Weber
What is the SI unit of inductance?
(A) Henry
(B) Farad
(C) Tesla
(D) Weber
What is the SI unit of magnetic flux?
(A) Weber
(B) Tesla
(C) Henry
(D) Farad
What is the SI unit of magnetic field strength?
(A) Tesla
(B) Ampere per meter
(C) Coulomb per meter
(D) Volt per meter
What is the SI unit of frequency?
(A) Hertz
(B) Second
(C) Minute
(D) Hour