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Your guide: Sir HamzaBelieves every formula has a story, and units never lie.
Your desk is 'long' and your exam fear is 'big'. Both sound like sizes. Yet only one of them can be checked with a ruler. What makes the difference?
We describe the world with many features: love, affection, fear, wisdom, beauty, length, volume, density, time and temperature. Some of them can be measured, directly or indirectly, with a tool or an instrument.
A ruler gives the length of an object, a clock gives the duration of an event, and a thermometer gives temperature, the degree of hotness. These are physical quantities. The laws of physics are written in them.
Love, fear and wisdom depend on the perception of the person observing them. No instrument reads them. They can be described in words, or compared using fixed criteria, indices or surveys. These are non-physical quantities.
Measurement: physical yes; non-physical no.
Instrument used: physical yes; non-physical no.
Number and unit: physical yes; non-physical no.
Examples: length, time · love, wisdom.
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Your desk is 'long' and your exam fear is 'big'. Both sound like sizes. Yet only one of them can be checked with a ruler. What makes the difference?
We describe the world with many features: love, affection, fear, wisdom, beauty, length, volume, density, time and temperature. Some of them can be measured, directly or indirectly, with a tool or an instrument.
A ruler gives the length of an object, a clock gives the duration of an event, and a thermometer gives temperature, the degree of hotness. These are physical quantities. The laws of physics are written in them.
Love, fear and wisdom depend on the perception of the person observing them. No instrument reads them. They can be described in words, or compared using fixed criteria, indices or surveys. These are non-physical quantities.
Measurement: physical yes; non-physical no.
Instrument used: physical yes; non-physical no.
Number and unit: physical yes; non-physical no.
Examples: length, time · love, wisdom.
A physical quantity can be measured with an instrument and written as a number with a unit. A non-physical quantity depends on the observer, so it can only be described or compared.
Q1. Your friend says, 'My exam fear is 7 out of 10.' Does the number make fear a physical quantity?
No. Fear stays non-physical; it is compared, not measured.
Q2. Short question 1.1 (p. 25): Can a non-physical quantity be measured? If yes, how?
Not measured with an instrument; only described or compared by criteria, indices or surveys.
Q3. Is the time a match lasts a physical quantity?
Yes. Time is physical: a clock gives it a number and a unit.
✗ Calling something physical because someone gave it a number, like a happiness score.
✓ Ask where the number came from. Only an instrument reading with a unit makes it physical.
✗ Saying a quantity is physical only if it can be read directly.
✓ The book says directly or indirectly. Density, for example, is found from other measurements.
✗ Thinking non-physical quantities have no use.
✓ They help us understand behaviour, emotions and social interactions; they are just not physics quantities.
1. Which one is a non-physical quantity?
(c) Wisdom depends on the observer and no instrument reads it; the other three are measured.
2. Temperature counts as a physical quantity because:
(a) An instrument gives it a number and a unit; feelings of heat differ from person to person.
3. Non-physical quantities can be compared using:
(d) Your book (p. 7) names pre-determined criteria, indices and survey techniques.
4. The laws and principles of physics are expressed through:
(b) The book says the foundation of physics rests on physical quantities (p. 6).
5. Love and fear depend mainly on:
(c) That is why they are non-physical: they have no instrument and no unit.
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