Physics · Units And Measurements · NEET
No. A physical quantity is the thing you measure (like length or mass). A unit is the fixed standard you compare it against (like metre or kilogram). When you measure, you get: physical quantity = number x unit. Example: length = 5 m. Here length is the physical quantity, 5 is the number, and metre (m) is the unit. The quantity is 'what', the unit is the 'yardstick'.
Writing just 5 has no meaning. 5 what - 5 metres, 5 seconds, 5 kilograms? The unit tells you which standard the number is counting. A measurement only makes sense as number + unit together. In NEET, an answer written without a unit (or with the wrong unit) is treated as wrong, so this habit protects easy marks.
Yes, temperature is a physical quantity because it can be measured and written as a number with a unit, like 37 degrees C or 310 K. Anything you can measure with an instrument and express as number x unit is a physical quantity - length, time, mass, current, temperature, and many more.
No. 'Beautiful' cannot be measured with an instrument or given a number and unit, so it is not a physical quantity. 'Fast' and 'hot' are vague feelings, but the measurable versions - speed (m/s) and temperature (K) - ARE physical quantities. The test is simple: can you measure it and write it as number x unit? If yes, it is a physical quantity.
Physics describes nature using exact, repeatable numbers instead of opinions. Measurement lets us compare, predict, and test laws. If one person says a rod is 'long' and another says 'short', there is no agreement. But if we measure 2.5 m, everyone in the world understands the same thing. Measurement turns physics into a precise science and lets formulas like v = u + at actually work with real values.
Try the real previous-year questions from this chapter — each with the answer and a full solution.
A physical quantity is anything in physics that you can measure and write as a number with a unit, such as length = 5 m or time = 10 s.
Every measurement has two parts: a number (how many) and a unit (of what). Example: in 12 kg, 12 is the number and kg is the unit.
Length (metre), mass (kilogram), and time (second) are common examples. Others include temperature, electric current, speed, and force.
Not always. Many physical quantities like mass and length are positive, but some, such as temperature in Celsius, charge, or a vector component, can be negative. The key is that it can be measured and given a number and unit.
Because the number alone does not tell you the standard it was compared with. '5' is meaningless until you say 5 metres, 5 seconds, or 5 kilograms. The unit gives the number its meaning.
