Conversion of Units from One System to Another

What is Unit Conversion?

Unit conversion is the process of converting a given value from one unit of measurement to another. It ensures uniformity and helps in comparing values across different measurement systems such as CGS (centimeter-gram-second), MKS (meter-kilogram-second), FPS (foot-pound-second), and SI (International System of Units).

Common Measurement Systems

• CGS: Uses centimeters, grams, and seconds.
• MKS: Uses meters, kilograms, and seconds.
• FPS: Uses feet, pounds, and seconds.
• SI: The modern and most widely used system (based on MKS).

Basic Unit Conversion Factors

• Length:
  • 1 m = 100 cm
  • 1 m = 3.2808 ft
  • 1 inch = 2.54 cm
• Mass:
  • 1 kg = 1000 g
  • 1 pound = 0.4536 kg
• Time:
  • 1 minute = 60 seconds
  • 1 hour = 3600 seconds
• Force:
  • 1 N (Newton) = 10⁵ dyne
  • 1 kgf (kilogram-force) = 9.8 N
• Pressure:
  • 1 atm = 101325 Pa
  • 1 Pa = 10 dyne/cm²
• Energy:
  • 1 Joule = 10⁷ erg

Tips for Converting Units

• Always write down the conversion factor before solving the problem.
• Use dimensional analysis or unit cancellation methods.
• Be cautious with square and cubic unit conversions (e.g., cm² to m² = divide by 10,000).
• Use scientific notation for very large or very small numbers.

Previous Year Questions

• SSC JE 2020: 1 Newton is equal to how many dyne?
• 1 N = 10⁵ dyne
• RRB JE 2019: Convert 5 meters to feet.
• 5 m × 3.2808 = 16.404 ft
• HSSC JE 2018: What is the value of 1 Joule in ergs?
• 1 Joule = 10⁷ erg

Conclusion

Mastering unit conversion is crucial for solving numerical problems and comparing results across different systems of measurement. With clear understanding and practice, conversions between CGS, MKS, FPS, and SI units become seamless, making physics both logical and universally applicable.