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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Long Answers - Answer Key

Differentiate between mass and weight, clarifying why ‘mass’ is the scientifically correct term for quantities like vegetables.

In physics, mass and weight are distinct concepts, though often used interchangeably in everyday language. Mass is defined as the quantity of matter contained within a body, representing its intrinsic property. Weight, on the other hand, is the force of gravity exerted on a body due to its mass. This means weight can change depending on the gravitational field (e.g., a person is weightless in space but still has mass). Therefore, while we commonly say a bag of vegetables “weighs 6 kg,” the scientifically precise statement is that its “mass is 6 kg,” because kilogram is a unit of matter quantity, not gravitational force.

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Outline the step-by-step procedure for determining the approximate area of a regular shape using graph paper.

To determine the approximate area of a regular shape using graph paper, begin by placing the flat surface of the object on the graph paper and carefully tracing its outline with a sharp pencil. Next, count the number of complete squares (typically 1 cm x 1 cm) that fall entirely within the traced outline. After that, identify and count the incomplete squares within the outline that are more than half covered by the shape. Crucially, any squares that are less than half covered should be completely ignored. Finally, add the total count of the complete squares to the total count of the incomplete squares that were more than half covered; this sum represents the approximate area of the object’s flat surface in square centimetres.

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Explain how an electronic balance works and state its advantages over a beam balance.

An electronic balance is a modern instrument used to measure mass, operating by converting the force exerted by the object’s mass into an electrical signal, which is then displayed as a digital reading. To use it, one simply places the object on its platform, and the mass value appears directly on the screen. A significant advantage of electronic balances over traditional beam balances is their high accuracy and sensitivity, allowing for precise measurements even of very small quantities. They are also much faster, providing instant readings without the need for manual balancing with standard weights, and often feature a ‘Tare’ function to zero out the container’s weight, simplifying measurements.

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Explain the importance of measurement in our daily lives and what makes a measurement value complete.

Measurement is essential in our daily lives, occurring everywhere from our homes to shops and doctor’s clinics. It allows us to quantify various aspects, such as the distance to school (length), the amount of sugar needed (mass), or the volume of milk to buy. A quantity that can be measured is termed a physical quantity. For any measurement value to be considered complete and correct, it must consist of two critical parts: a numerical value, which indicates ‘how much,’ and a unit of measurement, which specifies ‘what kind’ of quantity is being measured. Without both these components, a measurement is ambiguous and incomplete.

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Describe the key precautions one must take to ensure accurate length measurements using a ruler or metre scale.

To ensure accurate length measurements, several precautions are crucial. Firstly, the object being measured must always be placed on a flat, even surface, as an uneven surface can lead to incorrect readings. Secondly, the ruler or metre scale must be positioned exactly along the length of the object and kept as close as possible to it, avoiding any angles that would distort the measurement. Thirdly, the position of the eye is critical; it should be kept vertically above the point from where the measurement is being taken to prevent parallax error, often by keeping one eye shut. Lastly, if the ruler’s zero mark is worn out or unclear, measurement should begin from a clearly visible mark (e.g., 1 cm), and that initial reading must be subtracted from the final reading to obtain the object’s true length.

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