Vidaara.orgClass 11 · Physics
CodeVID-P11-01-SI-01
Units & the SI System — Assignment
Name: ____________________
Roll No.: __________
Date: ____________
General Instructions
- All questions are compulsory.
- Section A carries 1 mark each, Section B 2 marks, Section C 3 marks and Section D 5 marks.
- Show all working for Sections B, C and D. Only final answers are given at the end — for full solutions, raise your doubts with your teacher.
Section A — Multiple Choice Questions
5 × 1 = 5 marks
1.
The number of base units in the SI system is:
- A.5
- B.6
- C.7
- D.9
2.
The SI unit of luminous intensity is:
- A.lux
- B.candela
- C.lumen
- D.watt
3.
$1\\,\\text{nm}$ equals:
- A.$10^{-6}\\,\\text{m}$
- B.$10^{-9}\\,\\text{m}$
- C.$10^{-3}\\,\\text{m}$
- D.$10^{-12}\\,\\text{m}$
4.
Which is a supplementary SI unit?
- A.mole
- B.radian
- C.ampere
- D.kelvin
5.
The SI unit of pressure (pascal) in base units is:
- A.$\\text{kg m s}^{-2}$
- B.$\\text{kg m}^{-1}\\text{s}^{-2}$
- C.$\\text{kg m}^2\\text{s}^{-2}$
- D.$\\text{kg m}^{-2}\\text{s}^{-1}$
Section B — Short Answer (2 marks)
4 × 2 = 8 marks
6.
Convert $36\\,\\text{km h}^{-1}$ into $\\text{m s}^{-1}$.
7.
State the SI base units for current, temperature and amount of substance.
8.
Express $5\\,\\mu\\text{m}$ in metres.
9.
Why is a numerical value alone insufficient to specify a physical quantity?
Section C — Short Answer (3 marks)
4 × 3 = 12 marks
10.
Convert the density $13.6\\,\\text{g cm}^{-3}$ of mercury into $\\text{kg m}^{-3}$.
11.
Distinguish between fundamental and derived units with one example each.
12.
Express $1\\,\\text{newton}$ in CGS units (dyne), given $1\\,\\text{N} = 1\\,\\text{kg m s}^{-2}$.
13.
If the unit of length is tripled, what happens to the numerical value of a fixed volume?
Section D — Long Answer (5 marks)
2 × 5 = 10 marks
14.
Define the SI system. List all seven base quantities with their units and symbols, and state any three SI writing conventions.
15.
The acceleration due to gravity is $9.8\\,\\text{m s}^{-2}$. Express it in $\\text{km h}^{-2}$.
Answer Key
Section A — Multiple Choice Questions
- (C) 7
- (B) candela
- (B) $10^{-9}\\,\\text{m}$
- (B) radian
- (B) $\\text{kg m}^{-1}\\text{s}^{-2}$
Section B — Short Answer (2 marks)
- $10\\,\\text{m s}^{-1}$.
- ampere (A), kelvin (K), mole (mol).
- $5 \\times 10^{-6}\\,\\text{m}$.
- A unit is needed; the same magnitude gives different numbers in different units ($n \\propto 1/u$).
Section C — Short Answer (3 marks)
- $13600\\,\\text{kg m}^{-3}$.
- Fundamental: metre (length); derived: $\\text{m s}^{-1}$ (speed), built from base units.
- $1\\,\\text{N} = 10^{5}\\,\\text{dyne}$.
- It becomes $1/27$ of the original value.
Section D — Long Answer (5 marks)
- Length–metre (m), Mass–kilogram (kg), Time–second (s), Current–ampere (A), Temperature–kelvin (K), Amount–mole (mol), Luminous intensity–candela (cd). Conventions: no plural on symbols, space between number and unit, capitalise person-named symbols.
- $9.8 \\times \\tfrac{3600^2}{1000} = 127008\\,\\text{km h}^{-2}$.
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