Very Short Answer Questions in Units and Measurements

1) Define one astronomical unit

2) One micron = ________ meter

3) How many fermi are there in one meter

4) Write the abbreviation for RADAR, SONAR, and LASER

5) Obtain the Dimensional formula & give units for the following physical quantities.

a) Acceleration b) Areal Velocity c) Co-efficient of viscosity

d) Force e) Impulse f) Power g) Moment of Inertia

h) Young’s modulus

i) Gravitational Constant

j) Planck’s constant

6) Mention three physical quantities that have no dimensions.

7) Write the SI unit of temperature and electric current.

ANSWERS

1. One astronomical unit (AU) is the average distance between the sun and the earth.      i.e.   1 AU = 1.5 X 10¹¹ m
2. One micron = 1×10^-4 cm = 1×10^-6 m
3. One Fermi = 1×10^-15 m
4. RADAR – Radio wave Detection And Ranging

SONAR – Sound wave Detection And Ranging

LASER – Light Amplification by Stimulated Emission of Radiation

    5. a) Acceleration = Velocity/time – LT^-1

b) Areal Velocity = Area/time    – L²T^-1

c) Co-efficient of viscosity        – ML^-1T^-1

d) Force F = ma –   MLT^-2

e) Impulse = Linear momentum – MLT^-1

f) Power     = Work/time   – ML²T^-3

g) Moment of Inertia I = MR²– ML²

h) Young’s modulus = ML^-1T^-2

i) Gravitational Constant G – M^-1L³T^-2

j) Planck’s constant h – ML²T^-1

6. Physical quantities which don’t have dimension

1. Angle – M⁰L⁰T⁰ 
2. Strain – M⁰L⁰T⁰ (Strain = change in length/original length)
3. Relative density – M⁰L⁰T⁰ (density of the material/density of the water)

7. Temperature SI Unit – Kelvin

Current SI Unit – ampere.