Which of the following is equivalent to one kilo-Pascal ?
Try it first: pick an option, then read the explanation.
Asked in SSC JE 24.01.2018 (Morning Shift)
Detailed Explanation
The Pascal (symbol Pa) is the derived SI unit of pressure and stress, named after Blaise Pascal. Metric prefixes denote decimal multiples of the base unit.
1. Base SI unit definition of Pascal:
\[ 1\text{ Pa} = 1\text{ N/m}^2 \]
2. Metric prefix 'kilo' denotes a factor of \(10^3 = 1000\):
\[ 1\text{ kPa} = 10^3\text{ Pa} = 1000\text{ Pa} \]
3. Substitute the base unit definition:
\[ 1\text{ kPa} = 1000\text{ N/m}^2 \]
Why “1000 N/m²” Is Correct
Because the prefix 'kilo' represents one thousand (\(10^3\)), one kilo-Pascal is identically equal to \(1000\text{ Pascals}\), which equals \(1000\text{ N/m}^2\).
Why the Other Options Are Wrong
- B. 1000 N/mm²: 1000 N/mm² = 1000 × 10⁶ N/m² = 1,000,000 kPa = 1 GPa (gigapascal), which is one million times larger.
- C. 1000 N/cm²: 1000 N/cm² = 1000 × 10⁴ N/m² = 10,000 kPa = 10 MPa (megapascal), which is ten thousand times larger.
- D. 100 N/m²: 100 N/m² = 100 Pa = 1 hectopascal (1 hPa = 1 mbar), not 1 kPa.
Key Point
1 kPa = 1000 Pa = 1000 N/m² = 0.01 bar.
Key Concepts for Students
- 1 Pa = 1 N/m² is very small (roughly the pressure of a single sheet of paper resting on a table).
- Standard atmospheric pressure is 101.325 kPa = 101,325 N/m².
- 1 bar = 100 kPa = 10⁵ N/m² = 0.1 MPa.
Practice more: this is question 20 in Measurement of Pressure MCQs – Part 2. Try the whole set and check every answer instantly.