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

Chapter-wise Class 9 Advanced Science Solutions and NCERT Class 9 Advanced Science Chapter 1 Measurement Foundation of Science Question Answer are useful for focused study.

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:
FPS system and CGS system.

Question 2.
Why is SI system preferred over other systems?
Answer:
The SI system is preferred because

• It is universal used all over the world in science trade and industry.
• It is simple and consistent only one unit for each quantity (e.g. Metre for length and kilogram for mass).

Question 3.
Convert 250 N into g cm/s².
Answer:
1 N = 1 kg m/s²
= \(\frac{1000 \mathrm{~g} \times 100 \mathrm{~cm}}{\mathrm{~s}^2}\)
= 10⁵ g cm/s²
250 N = 250 × 10⁵ g cm/s²

Question 4.
Convert 1000 kg/L into kg/m³.
Answer:
1 m³ = 1000 L
1 L = \(\frac{1}{1000}\) m³
= 0.0001 m³
1000 kg/L = \(\frac{1000 \mathrm{~kg}}{\frac{1}{1000} \mathrm{~m}^3}\)
= 1000 × 1000 kg/m³
= 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
Answer:
(D) Foot is not an SI unit.

Question 2.
The SI unit of mass is
(A) gram
(B) kilogram
(C) pound
(D) tonne
Answer:
(B) Kilogram

Question 3.
Name the system of units used internationally.
Answer:
SI system (International system of units) or metric system.

Question 4.
Why is a common system of units necessary?
Answer:
A common system of units is necessary so that scientists, engineers and people all over the world can understand and compare measurements .easily. Without it, there will be confusion in communication, trade and scientific research.

Question 5.
Why is measurement necessary in physics?
Answer:
Measurement is necessary in physics to describe physical quantities accurately.

Question 6.
Why was there a need for a common system of units?
Answer:
Different countries used different units (like feet in USA and metre in India). This caused confusion and errors in international trade, scientific calculations and sharing data. So, a universal system was needed.

Question 7.
Explain the relation:
Magnitude = Numerical value × Unit.
Answer:
Any physical quantity is expressed as the product of number and a unit. The numerical value tells how many times the unit is contained in the quantity.
For example
If length = 5 m then,
numerical value = 5
Unit = metre

Question 8.
Why does the same classroom floor give different numerical values when measured with sticks of different lengths?
Answer:
The same classroom floor give different numerical values when measured with stick of different length, because the unit size is different. A longer stick (unit) will give a smaller numerical value and a shorter stick will give a larger numerical value for the same actual length.

Directions Q. Nos. 9 – 11: that are based on given activity (measuring classroom floor).
Suppose

Stick length	Length of wall	Breadth of wall
1 unit	30 units	20 units
2 units	15 units	10 units
3 units	10 units	6.6 units

Question 9.
Why are numerical values different?
Answer:
Numerical values are different because different units are used to measure the same quantity.

Question 10.
Is the actual size of the classroom different? Why or why not?
Answer:
No, the actual size of the classroom does not change. Only the numerical value changes because we are using different units. The real length and breadth remain the same.

Question 11.
What conclusion can you draw about units and measurement from this activity?
Answer:
The conclusion is

• The actual quantity does not depend on the unit.
• But the numerical value changes when we change the unit.
• A standard unit is necessary for proper comparison.

Question 12.
Fill in the blanks
(i) Measurement is the process of comparing an unknown quantity with a ___________ quantity.
Answer:
standard

(ii) The SI unit of mass is ___________.
Answer:
kilogram

(iii) In CGS system, the unit of length is ___________.
Answer:
centimeter

(iv) 1 km = ___________ m.
Answer:
100 m

(v) The modern internationally accepted system of units is called ___________.
Answer:
SI system

Question 13.
Match the following:

Column – A	Column – B
CGS	Pound
FPS	Kelvin
SI	Metre-kilogram-second
MKS	International system

Answer:

CGS	Kelvin (does not directly matched)
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 system of units, it would cause

• Great confusion in international trade
• Errors in scientific calculations.
• Difficulty in sharing scientific data and research.
• Problem in communication between scientists and engineers.
• Mistakes in buying/selling goods (wrong quantity delivered).

Question 15.
A scientist measures length of feet and another in metre. What difficulties may it lead to?
Answer:
It will be difficult to compare the two measurements directly.

The scientist will need to converts one unit into another unit, which can cause calculation errors and waste time. It creates confusion in understading the actual length.

Question 16.
If 1 metre was defined differently in different countries, what would happen to international trade?
Answer:
International trade would become very difficult and confusing. Manufactures and buyers would not agree on the exact sizes of products. This could lead to disputes, wrong deliveries and huge losses in business.

Question 17.
A shopkeeper sells rice using kilograms. A foreign customer asked for rice in pounds.
(i) Why is unit conversion necessary here?
(ii) If 1 kg = 2.2 pounds, how many pounds are there in 5 kg?
Answer:
(i) Because the shopkeeper uses kilograms while the customer understands pound. Conversion is needed so the customer gets the corrects quantity of rice he wants.

(ii) 1 kg = 2.2 pounds
5 kg = 5 × 2.2 pounds = 11 pounds

Measurement Foundation of Science Class 9 MCQ

Question 1.
The quantity having the same unit in all systems of units is
(A) mass
(B) time
(C) length
(D) temperature
Answer:
(B) time
Time is the quantity which has the same unit in all systems of units.

Question 2.
Which of the following is not a physical quantity?
(A) Time
(B) Impulse
(C) Mass
(D) Kilogram
Answer:
(D) Kilogram
Time, impulse and mass are physical quantities (things we measure). Kilogram is a unit to measure mass, not the quantity itself.

Question 3.
Unit of power is
(A) kilowatt
(B) kilowatt-hour
(C) dyne
(D) joule
Answer:
(A) kilowatt
Unit of power is kilowatt.

Question 4.
Which of the following system of unit is not based on units of mass, length and time alone.
(A) SI
(B) MKS
(C) FPS
(D) CGS
Answer:
(A) SI
SI system have seven basic units and two supplementary units.

Assertion-Reason Questions

Directions (Q.Nos. 1 – 3): In each of the following questions, a statement of Assertion is given by the corresponding statement of Reason. Mark the correct answer as
(A) Both Assertion and Reason are true and Reason is the correct explanation of Assertion.
(B) Both Assertion and Reason are true but Reason is not the correct explanation of Assertion.
(C) Assertion is true but Reason is false.
(D) Assertion is false but Reason is true.

Question 1.
Assertions (A): Mass is not a fundamental quantity.
Reason (R): Fundamental quantity are independent of the other physical quantities.
Answer:
(D) Assertion is false but Reason is true.

Question 2.
Assertion (A): Velocity is a derived quantity.
Reason (R): The unit of velocity is m/s².
Answer:
(C) Assertion is true but Reason is false.
The unit of velocity is m/s.

Question 3.
Assertion (A): 1 kilometer is equal to 1000 metre.
Reason (R): Kilometer is SI unit of length.
Answer:
(C) Assertion is true but Reason is false.

Measurement Foundation of Science Class 9 Extra Questions and Answers

Case/Source Based Questions

Directions (Q.No. 1): Answer the questions on the basis of your understanding of the following passage and related studied concepts.

Question 1.
A tailor is preparing to stitch a suit for a customer. He uses a measuring tape to find the length of the cloth required. He records the length as 2.5 metre Later, a student studying physics observes this and realises that the same length could also be expressed as 250 centimeter.

Give the answer.
i. In the measurement ‘2.5 metre’, identify the numerical value (n) and the unit (u).

ii. Explain why numerical value increased from 2.5 to 250 when the unit changed from metre to centimeter.

iii. What would happen to tailor’s business, if his metre tape stretched or shrank depending on the weather?
Answer:
i. Numerical value = 2.5,
Unit = metre

ii. The numerical value (n) is inversely proportional to the size of the unit
n ∝ \(\frac{1}{u}\)
Centimeters are a smaller unit than meters (1 m = 100 cm).
Because the unit decreased, the numerical value must increase proportionally to keep the actual length of the cloth the same. Since the unit become 100 times smaller, the number became 100 times larger (2.5 × 100 = 250).

iii. If the tailor’s tape changes with the weather, his measurement will be wrong, which is bad for business.

If the tape stretches:
The tailor gives away too much cloth for free. This causes a financial loss for him.

If the tape shrinks:

• The customer gets too little cloth.
• This leads to tight/badly fitted suits and unhappy customers.

Very Short Answer Type Questions

Question 1.
What is the physical quantity?
Answer:
A quantity which can be measured directly or indirectly and in terms of which the laws of physics can be expressed are called physical quantity.

Question 2.
Name any two derived quantities?
Answer:
Velocity, acceleration

Question 3.
What is the SI system?
Answer:
The system of units, which is accepted internationally for measurement is system international unit abbereriated as SI.

Question 4.
Write the unit of force?
Answer:
Newton

Question 5.
A bag of flour weighs 10 kg. If you need to label this for a customer who only understands the CGS system. What will be the weight of the flour in grams?
Answer:
1 kg = 1000 gm
10 kg = 10 × 1000 = 10000 gm

Short Answer Type Questions

Question 1.
What do you understand by the measurement? Define the physical unit?
Answer:
Measurement is the process of comparison of an unknown quantity with a known or standard quantity.
The standard amount of a physical quantity chosen to measure the physical quantity of the same kind is called a physical unit.

Question 2.
Define the fundamental quantities and derived quantities with examples.
Answer:
Fundamental quantities are independent of other quantities and are not defined in terms of other physical quantities,
e.g. Mass, length, time, temperature.

Derived quantities can be derived from fundamental quantities.
e.g. Velocity, acceleration etc.

Question 3.
What do you understand by FPS system and MKS system?
Answer:
FPS system:
It is the British engineering system of units, which uses foot as the unit of length, pound as the unit of mass and second as the unit of time.

MKS system:
It uses metre, kilogram and second as the fundamental unit of length, mass and time respectively.

Question 4.
Imagine you are measuring a pencil. You measure it as 15 cm and your friend measure it as 150 mm.
(i) Is the magnitude the same?
(ii) Which measurement uses a smaller unit?
Answer:
(i) Yes, the magnitude is exactly the same.
In physics, magnitude represents the actual amount or physical size of the object.

(ii) The measurement 150 mm uses the smaller unit.

Long Answer Type Questions

Question 1.
(i) What do you understand by physical unit?
(ii) What is the difference between fundamentals unit and derived unit?
Answer:
(i) The standard amount of a physical quantity chosen to measure the physical quantity of the same kind is called a physical unit.

(ii)

Fundamental unit	Derived unit
It can neither be derived from another nor can be further resolved into more simple unit.	It can be obtained from fundamental unit.

Question 2.
Write the SI units of following quantities: length, mass, time, electric current, thermodynamic temperature, amount of substance and luminous intensity.
Answer:

Quantity	Unit
Length	Metre
Mass	Kilogram
Time	Second
Electric current	Ampere
Temperature	Kelvin
Amount of substance	Mole
Luminous intensity	Candela

Question 3.
The process of modern science and global trade would be impossible without a common system of units. Give the answer of following questions
(i) Discuss three major problems that would arise, if every country continued to used its own local system of measurement.
(ii) Explain how the introduction of the SI system solved these problems?
Answer:
(i) If every country kept using its own different measurement system, these three major problems would happen

(a) Trade becomes difficult:
Buying and selling goods between countries would be very confusing. For example, 1 kg in one country may not match 1 kg in another country.

(b) Global cooperation is impossible:
Science, technology, space research and international projects would become very hard because everyone would speak in different “measurement languages.”

(c) Common problems cannot be solved together:
Issues like climate change, medicine, engineering and manufacturing would face big mistakes and delays because measurements would not match.

(ii) The introduction of the SI system solved these problems by providing a single, standard system of measurement used worldwide.
Earlier different countries used different system (CGS, FPS etc.) which caused confusion error and difficulty in communication. The SI system replaced these with uniform and well-defined units such as metre (m), kilogram and second.

In science, SI units made its easier to

• Compare experimental results.
• Communicate findings clearly.
• Avoid calculation mistakes.

In global trade, SI units ensured

• Fair measurement of years
• No confusion in weight, length or volume.
• Smooth international transactions.

Thus, the SI system brought accuracy, consistency, and global standardisation, solving the problem of multiple unit systems.

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