Units and Measurements

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A physical quantity is any quantity that can be measured. Examples: length, time. These are expressed as a numerical value followed by a unit, such as 5 m or 10 s.

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Fundamental quantities are independent physical quantities that cannot be defined in terms of other quantities. Three examples are: length, mass, and time.

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A derived quantity is obtained by combining fundamental quantities. Example: speed = distance/time. Its unit is m/s, derived from metre and second.

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In the SI system: length → metre (m), mass → kilogram (kg), time → second (s). These are standard units accepted globally for scientific measurements.

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Step 1: 1 km = 1000 m → 5 km = 5000 m Step 2: 1 m = 100 cm → 5000 m = 5000 × 100 = 500,000 cm Answer: 500,000 cm…

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Step 1: 1 hour = 60 minutes → 2 hours = 120 minutes Step 2: 1 minute = 60 seconds → 120 × 60 = 7200 seconds Answer: 7200 s…

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Accuracy refers to how close a measured value is to the true value. For example, if the actual length is 10.0 cm and a student measures 10.1 cm, it is more accurate than measuring 10.5 cm.

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Precision refers to how close repeated measurements are to each other. High precision means low variation between readings, even if they are not close to the true value.