Verified Solution • 2025–26 Session
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Q1.4: NCERT Physics - Part 1 UNITS AND MEASUREMENT 1.4 Solution: Explain this statement clearly: 'To call a dimensional quantity …
⚠️ Common Exam Traps & Conceptual Pitfalls
Students often fail to recognize that qualitative descriptors like 'large' or 'small' are physically meaningless without a reference standard; always reframe such statements by explicitly comparing the quantity to a specific, relevant reference value or by providing a dimensionless ratio.
Explain this statement clearly: 'To call a dimensional quantity large or small is meaningless without specifying a standard for comparison'. In view of this, reframe the following statements wherever necessary: (a) atoms are very small objects (b) a jet plane moves with great speed (c) the mass of Jupiter is very large (d) the air inside this room contains a large number of molecules (e) a proton is much more massive than an electron (f) the speed of sound is much smaller than the speed of light.
Step-by-Step Verified Solution
**Answer:** Every statement must specify a comparison standard.
**Step-by-Step Explanation:**
The statement means that saying a quantity is "large" or "small" has meaning only when compared to a standard reference.
Reframed statements:
- (a) Atoms are very small compared to a cricket ball.
- (b) A jet plane moves with a speed much greater than that of a car.
- (c) The mass of Jupiter is very large compared to the mass of the Earth.
- (d) The air inside this room contains a number of molecules much greater than the number of people in India.
- (e) A proton is about 1836 times more massive than an electron.
- (f) The speed of sound is about times smaller than the speed of light.
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