Unit – I E

Numerical Problems on System of Units: Numerical Problems

  1. Use standard prefixes used in S.I. system to express following quantities
    a) 106 phones b) 10-6 phones c) 1012 cows d) 10-9 monkeys e) 10-12 birds f)12×10-9 dogs g) 34 x 103 boys Numerical Problems
  2. Calculate number of kilometers in 20 miles using the conversion factors a mile = 5280 ft, 1 ft = 12 in, 1 in = 2.54 cm, 1 m = 100 cm, 1 km = 1000 m.
  3. Calculate the number of light years in one metre.
  4. Express 1 parsec in terms of light year Numerical Problems
  5. The mass of an electron is 9.1 x 10-31 kg. How many electrons would make 1 kg?
  6. The mass of an electron is 9.1 x 10-31 kg. How many electrons would make 1 g?
  7. The mass of a proton is 1.67 x 10-27 kg. How many protons would make 1 g?
  8. Express the distance between the sun and earth in parsec and light year.
  9. Derive the S.I. unit of joule (J) in terms of fundamental units.
  10. A new unit of length is chosen such that the speed of light in a vacuum is unity. What is the distance between the sun and the earth in terms of a new unit if it takes 8 minutes and 20 seconds to cover the distance
  11. If x = a + bt + ct2, where x is in metres and t is in seconds. Find units of a, b and c.
  12. Will the measure of a physical quantity depend on the system of units used?

Answers:

  1. a) 1 Mphones b) 1μphones c) Tcows d) nmonkeys e) pbirds f) 12  ndogs g) 34 kboys
  2. 32.187 km
  3. 1.057 x 10-16 light year
  4. 3.256 light years
  5.  1.1 x 1030
  6.  1.1 x 1027
  7. 5.99 x 1023
  8. 4.857 x 10-6 parsec, 1.581 x 10-6 light year
  9. kg m2s-2
  10. 500 new units
  11. unit of a = m, unit of b = m/s, unit of c = m/s2.

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