SI Base Units and Derived Units

Introduction

• Discussion about SI base units and derived units.
• Importance in scientific measurements.

SI Base Units

1. Length - Meter (m)
2. Mass - Kilogram (kg)
3. Time - Second (s)
4. Temperature - Kelvin (K)
5. Quantity - Mole (mol)
6. Electric Current - Ampere (A)
7. Luminous Intensity - Candela (cd)

Length Conversion Factors

• 1 km = 1000 m
• 1 m = 100 cm
• 1 mile = 1.609 km
• 1 mile = 5280 ft
• 3 ft = 1 yard
• 12 inches = 1 ft
• 1 inch = 2.54 cm

Mass Conversion

• 1 kg = 1000 g
• Chemistry typically uses grams; physics uses kilograms.

Time Units

• 60 s = 1 min
• 60 min = 1 hr
• 24 hr = 1 day
• 7 days = 1 week
• 30 days = 1 month
• 365 days = 1 year
• A light-year is a unit of distance, not time.

Temperature Conversion

• Celsius to Kelvin: K = °C + 273.15
• Celsius to Fahrenheit: °F = 1.8 × °C + 32

Mole

• Mole represents a large quantity, 6.02 × 10^23 (Avogadro's number).

Derived Units

Velocity

• Velocity (v) = Displacement / Time
• Unit: meters per second (m/s)

Acceleration

• Acceleration (a) = Change in velocity / Time
• Unit: meters per second squared (m/s²)

Force

• From Newton's Second Law: F = mass × acceleration
• Unit: Newton (N) = kg·m/s²

Area

• Area = length × width
• Unit: square meters (m²)

Volume

• Volume = length × width × height
• Unit: cubic meters (m³)
• 1 m³ = 1000 liters (L), 1 L = 1000 milliliters (mL)

Pressure

• Pressure = Force / Area
• Unit: Pascal (Pa) = N/m²
• Commonly measured in atmospheres (atm), tor, or mmHg in chemistry.
• 1 atm = 101.3 kPa = 760 tor = 760 mmHg

Density

• Density = Mass / Volume
• Chemistry: g/cm³ or g/mL
• Physics: kg/m³

Work and Energy

• Measured in Joules (J)
• Work = Force × Displacement
• Kinetic Energy: ½ mv²

Power

• Power = Work / Time
• Unit: Watt (W) = J/s
• 1 horsepower = 746 W
• Energy in kilowatt-hours (kWh) is a unit of energy, not power.

Momentum

• Momentum (p) = Mass × Velocity
• Unit: kg·m/s or N·s
• Impulse-momentum theorem: Impulse = Force × Time

Frequency

• Frequency = 1 / Period
• Unit: Hertz (Hz)

Electricity

Electric Current

• SI unit: Ampere (A)
• Electric Charge (Q) = Current (I) × Time (t)
• 1 A = 1 C/s

Electrical Resistance

• Resistance (R) = Voltage (V) / Current (I)
• Unit: Ohm (Ω)

Electric Potential

• Voltage is electric potential difference.
• 1 Volt (V) = 1 Joule (J) / Coulomb (C)

Key Takeaways

• Understand the distinction between base units and derived units.
• Familiarize with conversion factors and formulas for temperature, pressure, density, and energy.
• Recognize the units for electrical concepts and physical phenomena.