Measurement Foundation of Science Class 9 Question Answer Advanced Science Chapter 1

Students can use NCERT Class 9 Advanced Science Solutions Chapter 1 Measurement Foundation of Science Question Answer to understand complex concepts with ease.

Measurement Foundation of Science Class 9 Questions and Answers

Measurement Foundation of Science Question Answer Class 9

Quick Check

Question 1.
Name any two systems of units.
Answer:
Two commonly used systems of units are:

• CGS System: (Centimetre, Gram, Second)
• MKS System: (Metre, Kilogram, Second)

Question 2.
Why is the SI system preferred over other systems?
Answer:
The SI System (International System of Units) is preferred for several key reasons:

• Universal Acceptance: It is the standard system used globally in science, engineering, and trade, ensuring everyone uses the same measurements.
• Metric (Decimal) Base: It is based on powers of 10, making calculations and conversions (e.g, 1 km to 1000 m) much simpler than systems like FPS.
• Logical and Coherent: It uses a set of well-defined base units (like the metre and kilogram) from which all other units (like newton or joule) are derived consistently.

Question 3.
Convert 250 N into g-cm/s².
Answer:
We know: 1 N = 1 kg-m/s²
1 kg = 1000 g and 1 m = 100 cm
1 N = 1000 × 100 = 10⁵ g-cm/s²
250 N = 250 × 10⁵
= 2.5 × 10⁷ g-cm/s²

Question 4.
Convert 1000 kg/L into kg/m³.
Answer:
We know:
1 L = 10^-3 m³ So,
1 kg/L = 1 kg/(10^-3 m³)
= 10³ kg/m³
Therefore,
1000 kg/L = 1000 × 10³
= 10⁶ kg/m³

Check Your Understanding

Question 1.
Which of the following is not an SI unit?
(A) Metre
(B) Kilogram
(C) Second
(D) Foot
( Concept Applied Base units of SI
Answer:
Option (D) is correct.
Explanation: The SI (International System of Units) is a modern metric system that standardises measurements globally for scientific and professional use. The seven base SI units are metre (length), kilogram (mass), second (time), kelvin (temperature), ampere (electric current), mole (amount of substance), and candela (luminous intensity). The foot is a unit of length used in the Imperial system and the U.S. Customary system, but it is not part of the standardised SI framework.

Question 2.
The SI unit of mass is:
(A) Gram
(B) Kilogram
(C) Pound
(D) Tonne
Answer:
Option (B) is correct.
Explanation: Under the International System of Units (SI), the kilogram (kg) is the official base unit for mass. While units like the gram (g) and tonne (t) are metric and widely used in scientific calculations, they are considered derived or multiples of the base unit. The pound (lb) belongs to the Imperial system. Since 2019, the kilogram has been scientifically defined by the Planck constant (h), ensuring it remains a precise and universal standard for measurement across all fields of science.

Question 3.
Name the system of units used internationally.
Answer:
The internationally accepted system of units is the International System of Units, universally abbreviated as SI (from the Systeme International d’unites).

Question 4.
Why is a common system of units necessary?
Answer:
A common system of units is necessary for three primary reasons:
Global Standardisation: It ensures that measurements are uniform and consistent across different countries, preventing confusion in international trade and commerce.

Scientific Precision: It allows scientists and researchers worldwide to share data, replicate experiments, and communicate findings accurately without the need for complex conversions.

Error Prevention: It minimises the risk of costly and dangerous errors that occur when different systems (like Metric vs. Imperial) are used in engineering, aviation, and medicine.

Question 5.
Why is measurement necessary in physics?
Answer:
In physics, measurement is essential because it allows us to describe natural phenomena accurately and objectively. It replaces vague descriptions (like “hot” or “fast”) with precise numerical values. Since physics is a science based on laws and theories, measurement provides the quantitative data needed to verify these laws through experiments.

Question 6.
Why was there a need for a common system of units?
Answer:
A common system of units (SI) was needed to ensure global uniformity and accuracy. Before this, different regions used different scales, which led to confusion in trade, communication, arid scientific research. A universal system allows scientists and engineers from different countries to share data and collaborate without the risk of conversion errors.

Question 7.
Explain the relation: Physical Quantity = Numerical value × Unit.
Answer:
The magnitude of a physical quantity represents its total size or extent. It consists of two parts: a numerical value (n) and a unit (u).

• The unit is the standard used for comparison.
• The numerical value tells us how many times that unit is contained in the quantity.

For example, if a table is 2 metres long, 2 is the numerical value and metres is the unit. Without both, the measurement is incomplete and meaningless.

Question 8.
Why does the same classroom floor give different numerical values when measured with sticks of different lengths?
Answer:
This happens because the numerical value is inversely proportional to the size of the unit (n ∝ \(\frac{1}{u}\))

• If we use a shorter stick (smaller unit), we will have to repeat it more times to cover the floor, resulting in a larger numerical value.
• If we use a longer stick (larger unit), we repeat it fewer times, resulting in a smaller numerical value.

The actual physical size of the floor remains the same, but the “count” changes based on the size of the tool used.

Answer questions 9 to 11 that are based on Activity 1.1 (Measuring Classroom Floor)
Suppose:

Stick Length	Length of Wall	Breadth of Wall
1 unit	30 unit	20 unit
2 unit	15 unit	10 unit
3 unit	10 unit	6.6 unit

Question 9.
Why are numerical values different?
Answer:
The numerical values are different because the size of the unit (Stick Length) changes in each case. In measurement, the numerical value is inversely proportional to the size of the unit. As the stick length increases from 1 unit to 3 units, the number of times it fits into the wall decreases. For example, a 1-unit stick fits 30 times, but a 3-unit stick fits only 10 times.

Question 10.
Is the actual size of the classroom different? Why or why not?
Answer:
No, the actual size of the classroom is not different. The physical extent of the wall remains constant. The change in values is merely a change in the representation of that size. Mathematically, the product of the numerical value (n) and the unit (u) remain constant (n × u = constant):

• 1 × 30 = 30 (From Activity 1.1, I₁: I₂ : I₃ = 1 : 2 : 3)
• 2 × 15 = 30
• 3 × 10 = 30

Question 11.
What conclusion can you draw about units and measurement from this activity?
Answer:
We can draw the following conclusions:

• Measurement is a comparison: To measure a physical quantity, we compare it with a known standard (the unit).
• Inverse Relationship: The numerical value of a measurement depends on the unit chosen; a larger unit results in a smaller numerical value and vice versa (n ∝ \(\frac{1}{u}\))
• Need for Standardisation: Since different “sticks” (units) give different numerical results, there is a clear need for a standardised system of units (like SI units) so that everyone gets the same numerical value for the same physical size.

Question 12.
Fill in the blanks:
(a) Measurement is the process of comparing an unknown quantity with a _______ quantity.
(b) The SI unit of mass is ________.
(c) In CGS system, the unit of length is _________.
(d) 1 km = ________ m.
(e) The modern internationally accepted system of units is called _______.
Answer:
(a) Measurement is the process of comparing an unknown quantity with a known fixed (or standard) quantity.
(b) The SI unit of mass is the kilogram (kg).
(c) In the CGS system, the unit of length is centimetre (cm).
(d) 1 km = 1000 m.
(e) The modern internationally accepted system of units is called the International System of Units (SI).

Question 13.
Match the following:

Column A	Column B
CGS	Pound
FPS	International System
SI	Metre-Kilogram-Second
MKS	Gram

Answer:

Column A	Column B
CGS	Gram
FPS	Pound
SI	International System
MKS	Metre-Kilogram-Second

Question 14.
What problems might occur if every country used its own system of units for measurement?
Answer:
If every country used its own unique system of units, several significant problems would arise: Communication Barriers: Scientists and researchers would struggle to share data or replicate experiments, as every measurement would require complex conversions, increasing the risk of calculation errors.

Trade and Commerce Issues: International trade would become difficult and expensive. Buying and selling goods (like grain, oil, or machinery) would require constant recalculations of weight, volume and length, leading to disputes and financial losses.

Safety and Engineering Risks: In global projects— such as building aeroplanes, space missions, or medical equipment—using multiple systems can lead to catastrophic failures. A famous example is the Mars Climate Orbiter (1999), which was lost because one team used metric units while another used imperial units. Technological

Incompatibility: Parts manufactured in one country (like a simple screw or a smartphone component) would not fit devices made in another country, hindering global manufacturing and innovation.

Question 15.
A scientist measures length in foot and another in metre. What difficulties may it lead to?
Answer:
When one scientist measures in foot and another in metre, it creates a significant communication gap that can lead to critical errors in data interpretation and collaboration. Since these two units belong to different systems (Imperial and Metric), the researchers cannot directly compare their results without performing mathematical conversions. This increases the likelihood of calculation errors, where even a small rounding mistake during conversion can lead to incorrect conclusions or the failure of an experiment. Furthermore, if they are collaborating on a physical project, such as engineering a bridge or a spacecraft, parts designed using different units may not fit together, potentially resulting in catastrophic technical failures and wasted resources.

Question 16.
If 1 metre were defined differently in different countries, what would happen to international trade?
Answer:
If 1 metre were defined differently in different countries, international trade would descend into chaos and economic instability. Here are the primary consequences:

• Financial Disputes and Fraud: Buying and selling goods would become extremely difficult. For example, if a company in India ordered 1,000 metre of fabric from another country where the “metre” was shorter, they would receive less material than expected, leading to legal battles and loss of trust.
• Incompatibility of Products: Global manufacturing would collapse. A spare part for a car or a screw for a machine made in one country would not fit a product made in another, making global supply chains impossible.
• Massive Conversion Costs: Businesses would have to spend huge amounts of time and money on complex calculations and specialised tools to adjust to each country’s specific definition, making products much more expensive for consumers.
• Technical Failures: In construction and engineering projects involving multiple nations (like international pipelines or bridges), differing definitions of a metre could lead to structural misalignments, rendering projects unsafe or unusable.

Question 17.
A shopkeeper sells rice using kilograms. A foreign customer asks for rice in pounds.
(a) Why is unit conversion necessary here?
(b) If 1 kg = 2.2 pound, how many pounds are there in 5kg?
Answer:
(a) Unit conversion is necessary because the shopkeeper and the customer are using two different systems of measurement (Metric and Imperial). To ensure a fair and accurate transaction, they must communicate in a common “language.” Conversion allows the shopkeeper to translate the customer’s request into the units used by their weighing scale, preventing any misunderstanding or financial loss for either party.

(b) To find the weight in pounds, we multiply the weight in kilograms by the conversion factor:
Weight in pounds = Weight in kg × 2.2
Weight in pounds = 5 × 2.2 = 11 pound
There are 11 pounds in 5 kg.

Measurement Foundation of Science Class 9 Extra Questions and Answers

Short Answer Type Questions

Question 1.
Why is it impossible to measure the “weight” of a length or the “length” of a temperature?
Answer:
Measurement is fundamentally a systematic process of comparing an unknown quantity with a known standard unit of the exact same nature. Because length, weight, and temperature represent entirely different physical quantities, they lack a common basis for comparison. We can only compare and measure physical quantities those are of the same kind.

Question 2.
State any two major problems that scientists and traders faced globally before the adoption of a common system of units.
Answer:
Without a universal standard, international trade suffered from massive confusion because product weights and lengths did not match across borders. Additionally, scientific collaboration was highly prone to errors, as calculations performed in one regional system (like FPS) were frequently miscalculated or distorted when converted to another system (like MKS).

Question 3.
Compare the CGS, FPS, and MKS systems of units based on how they measure fundamental quantities. Which physical quantity remains uniquely consistent across all three?
Answer:
The three historical systems differ based on their chosen base units for length and mass: the CGS system uses centimetre (cm) and gram (g), the FPS system uses foot (ft) and pounds (lb), and the MKS system uses metre (m) and kilogram (kg). Despite these regional variations in spatial and mass standards, time is the single physical quantity that remains completely uniform, as all three frameworks utilise the second (s) as their standard unit of duration.

Question 4.
Explain the significance of the SI System in modern science and trade, and highlight two distinct advantages that led to its global adoption.
Answer:
The International System of Units (SI) serves as a universal scientific language that ensures measurements mean the exact same thing everywhere on Earth, eliminating cross-border errors. Its first major advantage is that it is strictly standardised and universal, allowing seamless global trade and data sharing. Its second advantage is that it is highly logical and metric, relying on a decimal system (powers of 10) which makes mathematical conversions between units incredibly simple compared to older systems.

Question 5.
Explain why physics is considered a quantitative science and justify how accurate measurement serves as its foundation.
Answer:
Physics is a quantitative science because it relies on precise, numerical data rather than qualitative descriptions to explain how the universe works. Accurate measurement provides the objective data necessary to test theories, calculate exact dimensions, and track the duration of events. Without this quantitative precision, scientific results would be unreliable, inconsistent, and impossible to verify or replicate globally.

Question 6.
Using the example of two scientists—one in India and one in the USA—explain how the lack of a universal unit standard impacts scientific research and data sharing.
Answer:
When scientists use different regional standards— such as one measuring length in metres and the other in foot—comparing data becomes difficult and highly error-prone. The lack of a shared system requires constant mathematical conversions, which increases the likelihood of calculation mistakes. A universal standard like the SI system solves this problem by ensuring all scientists ‘speak the same language/ allowing for seamless, accurate global collaboration.

Question 7.
Analyse the historical transition of unit systems by explaining how the MKS system paved the way for modern international standards.
Answer:
The MKS (Metre-Kilogram-Second) system standardised larger, highly practical baseline values for length and mass, making it much more suitable for industrial applications than lab-scale systems like the CGS. Because of this practical scale, it became the trusted foundation for modern engineering. Recognising its consistency and efficiency, international committees used the MKS framework as the direct baseline to evolve and build the modern SI system used worldwide today.

Long Answer Type Questions

Question 1.
A global aerospace engineering firm is manufacturing components across three different facilities located in the United Kingdom, Japan, and the United States.
(a) Define the systematic process of measurement and identify the SI units and symbols for the five physical quantities: Length, Mass, Time, Temperature, and Electric Current.
(b) Analyse the historical problems this engineering firm would face if their regional facilities insisted on using the, FPS, CGS, and MKS systems respectively.
(c) State two distinct mathematical and practical advantages that the global adoption of the SI system provides to prevent catastrophic failures in such international engineering projects.
Answer:
Measurement is the systematic process of comparing an unknown physical quantity with a known, standardised quantity (the unit) of the exact same nature.
SI Units and Symbols Table:

Physical Quantity	SI Base Unit	Official Symbol
Length	Metre	(m)
Mass	Kilogram	(kg)
Time	Second	(s)
Temperature	Kelvin	(K)
Electric Current	Ampere	(A)

(b) If th facilities used different historical systems, severe manufacturing errors would occur because their baseline units conflict:

• The UK Facility (FPS): Would design blueprints using the foot for length and the pound for mass.
• The Japan Facility (CGS): Would calculate laboratory metrics using tiny scales like the centimetre and the gram, making large-scale parts difficult to map out.
• The US Facility (MKS): Would track specifications in metre and kilogram.
• Impact: Attempting to assemble a high-precision aircraft when parts are calculated across foot, centimetre, and metre would lead to massive assembly mismatches, math conversion slip-ups, and severe financial losses.

(c) The global adoption of the SI system eliminates these risks through two main advantages:

• It is Logical and Decimal-Based (Metric): All conversions are based on clean powers of 10, making calculations straightforward and drastically lowering human mathematical error compared to complex regional systems (like converting foot to inches).
• It is Rigidly Standardised and Universal: It ensures that a “metre” or a “kilogram” is identical in every country on Earth, allowing international teams to collaborate seamlessly and manufacture parts that fit perfectly every single time.

Case-Based Questions

I. Before the global adoption of the International System of Units (SI), a major international aerospace project suffered a catastrophic failure due to a communication breakdown between two engineering teams. The manufacturing facility in the United States calculated the thruster engine data using the historical British Foot-Pound-Second (FPS) system, tracking critical mechanical forces in pounds. Conversely, the navigation software design team in Europe expected the incoming trajectory data to be formatted in the metric Metre-Kilogram-Second (MKS) system, which forms the direct foundation of modern SI units. Because the mathematical conversion between the two regional systems was overlooked, the spacecraft approached its target planet at an incorrect altitude and was completely destroyed in the atmosphere. This multi-million-dollar disaster highlighted that physics is a strictly quantitative science where accurate, universally standardised data sharing is mandatory for survival.

Question 1.
Why did the spacecraft encounter a catastrophic failure during its mission?
(A) The navigation software experienced a sudden hard-ware power failure.
(B) The teams used conflicting systems of units, causing a critical data conversion error.
(C) The thruster engines lacked the mechanical capacity to operate in space.
(D) The atmospheric density of the target planet was calculated incorrectly by both teams.
Answer:
Option (B) is correct.
Explanation:
The passage explicitly states the failure happened because one team used the FPS system while the other expected the MKS system, and the conversion between them was completely overlooked.

Question 2.
Which fundamental baseline unit was the European software team expecting for length measurements based on their system?
(A) Foot
(B) Centimetre
(C) Metre
(D) Kilogram
Answer:
Option (C) is correct.
Explanation:
The European team used the MKS (Metre- Kilogram-Second) system, where the standard baseline unit for length is the metre.

Question 3.
According to the passage and your understanding of measurement systems, which physical quantity would have recorded identical numerical values across both teams frameworks without needing any conversion?
(A) Mass
(B) Length
(C) Force
(D) Time
Answer:
Option (D) is correct.
Explanation:
Both the FPS (Foot-Pound-Second) and MKS (Metre-Kilogram-Second), systems share the exact same base unit for time: the second.

Question 4.
What key advantage of the modern SI system would have directly prevented this international engineering disaster?
(A) It relies on complex fractional systems that make re-gional equations more specialised.
(B) It is universally standardised, ensuring all global teams speak the exact same language of measurement.
(C) It uses completely distinct base units for every indi-vidual country to preserve regional traditions.
(D) It prioritises laboratory-scale CGS metric conversions over industrial engineering applications.
Answer:
Option (B) is correct.
Explanation:
The SI system provides a universal, uniform standard worldwide, which eliminates regional conversion mistakes and ensures global consistency.

Measurement Foundation of Science Class 9 MCQ

Question 1.
A lab technician measures the mass of a chemical sample to be 45 grams and the duration of its reaction to be 12 seconds. Which historical system of units is directly aligned with these specific measurements?
(A) The FPS System
(B) The MKS System
(C) The CGS System
(D) The SI System
Answer:
Option (C) is correct.
Explanation: The CGS system stands for centimetre (length), gram (mass), and second (time). Since the technician recorded the mass in grams (g) and the time in seconds (s), this practice perfectly corresponds to the CGS framework.

Question 2.
Consider the standard units mentioned in the text. Which of the following sets correctly pairs the physical scenario with its appropriate standard unit?
(A) Tailor shop → Kilogram, Grocery store → Metre
(B) Race track → Degree Celsius, Clinic → Second
(C) Tailor shop → Metre, Grocery store → Kilogram
(D) Clinic → Metre, Race track → Kilogram
Answer:
Option (C) is correct.
Explanation: According to the texts reference table, length of cloth at a tailor shop is evaluated in metres (m), while the quantity of a solid commodity like rice at a grocery store is measured using mass in kilograms (kg).

Question 3.
According to the foundational principles of measurement, why is it physically impossible to determine the ‘length’ of a temperature?
(A) Length is a derived quantity, whereas temperature is always considered an absolute standard.
(B) Measurement requires comparing an unknown quantity with a known standard of the exact same nature.
(C) Temperature fluctuates too rapidly to be fixed along-side a physical spatial dimension.
(D) The CGS system does not contain a defined scalar val-ue for tracking ambient thermal changes.
Answer:
Option (B) is correct.
Explanation: Measurement is defined as the systematic process of comparing an unknown quantity with a known standard unit of the same nature. Because length (spatial dimension) and temperature (thermal state) are entirely different kinds of physical quantities, they cannot be compared or cross-measured.

Question 4.
Before the global adoption of the International System of Units (SI), international trade and scientific collaboration frequently suffered from data miscalculations. What was the primary root cause of these errors?
(A) The absolute lack of tools capable of measuring time in seconds across different continents.
(B) The difficulty of performing conversions and comparing data between multiple conflicting regional standards.
(C) A widespread global scientific disagreement over whether physics should be a quantitative science.
(D) The mathematical instability inherent to the MKS system before it evolved into engineering standards.
Answer:
Option (B) is correct.
Explanation: Having multiple unique regional systems (like MKS, CGS, and FPS) caused massive confusion because calculations performed in one system were easily miscalculated or distorted during conversion to another, making global data-sharing error-prone.

Question 5.
Match the physical quantities, scenarios, or measurement systems listed in Column I with their appropriate units or definitions provided in Column II. Choose the option that represents the correct matching sequence.

Column I	Column II
(A) Quantities of the same kind	(1) FPS System baseline unit for mass
(B) Pound (lb)	(2) System that evolved into modern SI units
(C) Duration of a sprint	(3) Mandatory condition for any valid measurement comparison
(D) MKS System	(4) Measured uniformly in seconds across CGS, FPS, and MKS

(A) (A) → (3), (B) → (1), (C) → (4), (D) → (2)
(B) (A) → (2), (B) → (4), (C) → (1), (D) → (3)
(C) (A) → (3), (B) → (4), (C) → (1), (D) → (2)
(D) (A) → (1), (B) → (3), (C) → (2), (D) → (4)
Answer:
Option (A) is correct.
Explanation: The matching sequence is determined by evaluating the core rules and historical systems of measurement. First, item (A) matches with (3) because the fundamental rule of measurement states that we can only systematically compare physical quantities that share the exact same nature or kind. Second, item (B) matches with (1) because the pound (lb) serves as the historical baseline unit of mass specifically within the British Foot-Pound- Second (FPS) system.

Third, item (C) matches with (4) because time intervals, such as the duration of a race track run, are uniquely consistent across all three historical systems (CGS, FPS, and MKS), which all share the second (s) as their standard unit. Finally, item (D) matches with (2) because the Metre-Kilogram-Second (MKS) system provided the standardised baseline for modern engineering, which directly laid the groundwork for and evolved into the universally accepted International System of Units (SI) used globally today.

Assertion-Reason Questions

Directions: In the following questions, a statement of Assertion (A) is followed by a statement of Reason (R). Mark the correct choice as:
(A) Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A).
(B) Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of Assertion (A).
(C) Assertion (A) is true, but Reason (R) is false.
(D) Assertion (A) is false, but Reason (R) is true.

Question 1.
Assertion (A): The historical Foot-Pound-Second (FPS) system was widely phased out in global scientific data- sharing in favour of a unified system.
Reason (R): Calculations performed across multiple conflicting regional standards were highly prone to miscalculations and conversion errors.
Answer:
Option (A) is correct.
Explanation: The assertion is true because regional systems like the FPS system caused widespread confusion in international science and trade. The reason correctly explains why it was phased out, as a single, universal system (SI) was developed to prevent critical conversion errors.

Question 2.
Assertion (A): If a scientist in India records a time interval using the MKS system and a scientist in the USA records it using the CGS system, comparing their base time data is exceptionally difficult.
Reason (R): The standard base unit for measuring duration or time is the “second” across the CGS, FPS, and MKS systems. * 0
Answer:
Option (D) is correct.
Explanation: The assertion is false because time is the physical quantity that is uniformly measured in ‘second’ across all three historical systems, making the data identical and very easy to compare. The reason is a completely true statement on its own.

Question 3.
Assertion (A): A global trader cannot systematically compare or evaluate a shipment of rice measured in” kilograms against a roll of textile measured in metres.
Reason (R): Valid physical measurement requires comparing an unknown quantity with a known standard unit that shares the exact same nature.
Answer:
Option (A) is correct.
Explanation: The assertion is true because mass and length are completely different physical quantities. The reason provides the correct scientific explanation because a comparison is only mathematically valid if the quantities being evaluated share the same nature.