Physical quantities and units
Section: Physical Quantities and Units | Syllabus: Cambridge AS Level Physics 9702
Physical Quantities A physical quantity is a property of an object or phenomenon that can be measured. Every physical quantity consists of two parts: a numerical magnitude and a unit . Physical Quantity Magnitude × Unit (e.g., 5.0 kg) Important A number without a unit has no physical meaning in this context.
For example, saying a length is "5" doesn't tell us if it's 5 meters or 5 kilometers. Common Estimates Candidates are expected to make reasonable estimates of physical quantities. Here are some common reference values: Quantity Reasonable Estimate Mass of an adult 70 kg Height of an adult 1.7 m Mass of an apple 100 g (0.1 kg) Thickness of a sheet of paper 0.1 mm Speed of sound in air 330 m s^-1 Weight of an adult 700 N
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