General Physics Lecture Notes: Measurements

Instructor Introduction

• Instructor: Mr. Belty Cruz
• Course: General Physics 1
• Topic: Measurements

Learning Objectives

1. Solve measurement problems involving unit conversions.
2. Express units of measurement in scientific notation.

Definitions of Measurement

• Measurement: Numbers that describe living and non-living things.
• Quantitative Description: A fundamental property or physical phenomenon.
• Quantities Described: Length, weight, area, volume, and time.
• Comparison: Physical quantity compared with a standard.

Systems of Measurements

Historical Systems

• Obsolete Local Systems: Use of body parts for measurement.
  • Cubit: Distance from elbow to middle finger.
  • Palm: Width of a person's fingers (excluding thumb).
  • Yard: Distance from nose tip to middle finger tip.
  • Instruments: Sundials for measuring time.
• Non-standard Units: Various local units used in different cultures.
  • Examples include dhamma, dali, talam pakhan, etc.

Modern Systems

• Metric System: Widely used in Europe and the rest of the world.
• Imperial System: Commonly used in the USA.
  • British System: Formalized in 1824 for industrial consistency.
  • Common Units: Pounds, ounces, miles, yards, pints, gallons, etc.

Metric vs. Imperial System

• Metric System: Based on multiples of 10, easier for calculations.
• International System (SI): Modern form of the metric system.
• Prefix Examples:
  • Deci (10^-1), Yokta (10^-24)

SI Units and Base Quantities

Fundamental Quantities

1. Length: Meter (m)
   • Defined by the speed of light in vacuum.
2. Mass: Kilogram (kg)
   • Defined by Planck's constant.
3. Time: Second (s)
   • Defined by the oscillation of cesium atoms.
4. Temperature: Kelvin (K)
   • Defined by Boltzmann's constant.
5. Luminous Intensity: Candela (cd)
   • Defined by luminous efficacy.
6. Electric Current: Ampere (A)
   • Defined by the elementary charge.
7. Amount of Substance: Mole (mol)
   • Contains 6.02 x 10^23 particles (Avogadro's number).

Derived Quantities and SI Units

• Area: m²
• Volume: m³
• Density: kg/m³
• Velocity: m/s
• Force: N (Newton)
• Pressure: N/m²
• Acceleration: m/s²

Sample Problems

Conversion Examples

1. 20 meters to kilometers:
   • 20 m x (1 km / 1000 m) = 0.02 km = 2 x 10^-2 km
2. 50 seconds to minutes:
   • 50 s x (1 min / 60 s) = 0.83 min = 8.3 x 10^0 min
3. 100 megahertz to hertz:
   • 100 MHz x (1 x 10^6 Hz / 1 MHz) = 1 x 10^8 Hz
4. 45 microhertz to millihertz:
   • 45 x 10^-6 Hz x (1 x 10^-3 mHz / 1 x 10^-6 uHz) = 4.5 x 10^-2 mHz
5. 15 m/s to km/h:
   • 15 x (1 km / 1000 m) x (3600 s / 1 h) = 54 km/h = 5.4 x 10^1 km/h

Example of Squared Units

1. 55 m² to ft²:
   • (55 m²) x (3.28² ft² / 1 m²) = 5.92 x 10² ft²
2. 120 m/s² to km/h²:
   • (120 m/s²) x (1 km/1000 m) x (1.30 x 10^7 s²/1 hr²) = 1.6 x 10^6 km/hr²

Conclusion

• Application of these units and conversions is crucial in physics and daily life. Practice with these conversions will aid in mastering measurement concepts.