Answer key

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Last edited 26 days ago by Learn LoopHQ.

Chapter: 02. Physical Quantities And Measurement 1

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Physical Quantities and Measurement - 1: Answer Key

Section A: Multiple Choice Questions (MCQs)

c) Metre

c) Millimetre

b) Resets the reading to zero, ignoring the container’s weight

b) Parallax error

d) Area

Section B: Fill in the Blanks

physical quantity

unit

100

kilogram

Area

Section C: True or False

False

False (You multiply by 1000)

True

False

Section D: Short Answer Questions

Every measurement value consists of a numerical value (number) and a unit of measurement.

Two instruments commonly used to measure length are the ruler and the measuring tape.

You should avoid placing an object on an uneven surface because it can cause the measurement to be inaccurate or incorrect.

The SI unit of area is the square metre (m²).

The National Physical Laboratory (NPL) in New Delhi is responsible for maintaining the national standards for all the basic units in India, like the standard metre and kilogram.

Section E: Diagram-Based Questions

Eye positions A and C would give an incorrect measurement reading because they are not directly perpendicular to the measurement mark.

The correct length of the red block as indicated in the image is 6.2 cm (shown at eye position B).

The name given to the error caused by incorrect eye positioning during measurement is parallax error.

Section F: Long Answer Questions

The International System of Units (SI units) was introduced to overcome the inconsistencies and variations caused by older measurement methods, such as using body parts. Since body part lengths differed from person to person, results were inconsistent. SI units provide a worldwide accepted, standardized system, ensuring uniform and reliable measurements globally.

Mass is the quantity of matter in a body, while weight is the force of gravity acting on that mass. For example, a bag of vegetables has a certain mass (e.g., 6 kg), which is constant regardless of location. However, its weight would change if measured on the moon where gravity is different. Thus, ‘mass’ is the scientifically more appropriate term for describing the quantity of matter in the vegetables.

To measure the approximate area of an irregular leaf using graph paper, you would place the leaf on the graph paper and carefully trace its outline. Then, count all the complete squares fully enclosed within the outline. Next, count the incomplete squares that are more than half covered by the leaf’s outline, ignoring any squares that are less than half covered. Finally, sum the total count of the complete squares and the more-than-half covered squares to get the approximate area.

Section G: Identifying and Differentiating Concepts

a) The amount of rice in a bag: Mass b) The height of your classroom door: Length c) The thickness of a book: Length d) The weight of a fruit: Mass (scientifically, though ‘weight’ is used commonly)

A multiple of a standard unit is a larger unit derived by multiplying the standard unit by a power of ten. For example, a kilometre (km) is a multiple of a metre (m), as 1 km = 1000 m. A submultiple is a smaller unit derived by dividing the standard unit by a power of ten. For example, a centimetre (cm) is a submultiple of a metre (m), as 1 m = 100 cm.

Section H: Everyday Use and Awareness

When buying vegetables at a market, I should check two things related to the weighing scale and weights:

I should ensure the beam balance is properly balanced and the pointer is at the center when empty.

I should check that the standard weights used by the shopkeeper have an intact lead seal with the stamp of the Weights and Measures Department.

Growing plants in a school garden is important for environmental awareness for two main reasons:

Plants produce oxygen, which is vital for breathing, and absorb carbon dioxide, helping to reduce greenhouse gases.

They help prevent soil erosion and support local biodiversity, contributing to a healthier and more sustainable environment.

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