Constants

Important Constants in Physics

Constants are fundamental values that remain the same in all scientific calculations. Below are some key physical constants you need to know for NSC Physical Sciences.

Key Constants and Their Values

Motion and Gravity

• Acceleration due to gravity (g) = 9.8 m/s²
  • Objects accelerate by 9.8 m/s every second when falling.
• Gravitational constant (G) = 6.67 × 10⁻¹¹ N·m²/kg²
  • Used in Newton's Law of Universal Gravitation to calculate gravitational force.

Speed and Light

• Speed of light (c) = 3 × 10⁸ m/s
  • Light travels 300 million metres per second.
• Speed of sound in air = 340.29 m/s – 343 m/s
  • Sound takes about 3 seconds to travel 1 kilometre.

Fundamental Quantum Constants

• Planck's constant (h) = 6.626 × 10⁻³⁴ J·s
  • Used in quantum mechanics, relating energy to frequency.
• Charge of an electron (e) = 1.6 × 10⁻¹⁹ C
  • The fundamental unit of electric charge.

Atomic and Gas Constants

• Mass of an electron (mₑ) = 9.11 × 10⁻³¹ kg
• Mass of a proton (mₚ) = 1.67 × 10⁻²⁷ kg
  • Protons are much heavier than electrons.
• Gas constant (R) = 8.31 J/mol·K
  • Appears in the ideal gas equation: PV = nRT.
• Molar volume of a gas (Vₘ) = 22.4 L/mol at STP
  • One mole of gas occupies 22.4 litres at standard conditions.

Electrostatics

• Coulomb's Law constant (k) = 9 × 10⁹ N·m²/C²
  • Determines the force between electric charges.

Quick Tips for Remembering Constants

✔ Speed of light is always 3 × 10⁸ m/s – fastest possible speed.

✔ Gravitational acceleration (g) ≈ 10 m/s² – useful for quick calculations.

✔ Planck's constant (h) is extremely small – important in quantum physics.

✔ Electron charge is always negative (-1.6 × 10⁻¹⁹ C).