Essential Physics Formulas and Concepts

Posted on May 29, 2025 in Physics

Energy Principles and Equations

Kinetic Energy (J) = ½ × Mass (kg) × Speed (m/s)² → Ek = ½mv²

Gravitational Potential Energy (J) = Mass (kg) × Gravitational Field Strength (N/kg) × Height (m) → Ep = mgh

Elastic Potential Energy (J) = ½ × Spring Constant (N/m) × Extension² (m) → E = ½ke²

Change in Thermal Energy (J) = Mass (kg) × Specific Heat Capacity (J/kg°C) × Temperature Change (°C) → ∆E = mc∆θ

Rate of Doing Work and Power

  • Power (W) = Energy Transferred (J) / Time (s) → P = E/T
  • OR
  • Power (W) = Work Done (J) / Time (s) → P = W/T

Efficiency = Useful Power Output / Total Power Input

Electricity Formulas and Laws

Current flows from positive (+) to negative (-).

Charge (C) = Current (A) × Time (s) → Q = IT

Ohm’s Law

Potential Difference (V) = Current (A) × Resistance (Ω) → V = IR

Resistor and Current Rules

  • Resistors in Series: Rtotal = R1 + R2 + R3…
  • Resistors in Parallel: 1/Rtotal = 1/R1 + 1/R2 + 1/R3…
  • Current in Series: I1 = I2 = I3… (Current is the same everywhere)
  • Current in Parallel: Itotal = I1 + I2 + I3… (Total current is the sum of branch currents)

Energy Transferred (J) = Charge Flow (C) × Potential Difference (V) → E = QV

Power (W) = Potential Difference (V) × Current (A) → P = VI

Transformer Equation

Potential Difference across Secondary Coil (V) × Current through Secondary Coil (A) = Potential Difference across Primary Coil (V) × Current through Primary Coil (A) → VsIs = VpIp

Particle Model of Matter Equations

Density (kg/m³) = Mass (kg) / Volume (m³) → ρ = m/V

Specific Latent Heat: Energy (J) = Mass (kg) × Specific Latent Heat (J/kg) → E = mL

Forces and Motion Equations

Weight (N) = Mass (kg) × Gravitational Field Strength (N/kg) → W = mg

Work Done (J) = Force (N) × Distance (m) → W = Fs

Hooke’s Law

Force (N) = Spring Constant (N/m) × Extension (m) → F = ke

Elastic Potential Energy (J) = ½ × Spring Constant (N/m) × Extension² (m) → Ee = ½ke²

Spring Combinations

  • Springs in Parallel: Total Spring Constant (N/m) = Sum of individual spring constants → ktotal = k1 + k2 + k3…
  • Springs in Series: Reciprocal of Total Spring Constant (N/m) = Sum of reciprocals of individual spring constants → 1/ktotal = 1/k1 + 1/k2 + 1/k3…

Moment of Force (Nm) = Force (N) × Perpendicular Distance from Pivot (m) → M = Fd

Pressure (Pa) = Force (N) / Area (m²) → p = F/A

Pressure in Liquid (Pa) = Height of Column of Liquid (m) × Density of Liquid (kg/m³) × Gravitational Field Strength (N/kg) → p = hρg

Gas Laws

  • Gay-Lussac’s Law: Pressure 1 (Pa) / Temperature 1 (K) = Pressure 2 (Pa) / Temperature 2 (K) → P1/T1 = P2/T2
  • Boyle’s Law: Pressure 1 (Pa) × Volume 1 (m³) = Pressure 2 (Pa) × Volume 2 (m³) → P1V1 = P2V2
  • Dalton’s Law of Partial Pressures: Total Pressure (Pa) = Pressure of Gas 1 (Pa) + Pressure of Gas 2 (Pa) + Pressure of Gas 3 (Pa)… → Ptotal = Pgas1 + Pgas2 + Pgas3…

Kinematics and Dynamics

Distance (m) = Speed (m/s) × Time (s) → s = vt

Acceleration (m/s²) = Change in Velocity (m/s) / Time (s) → a = ∆v/t

Newton’s Equations of Motion

  1. Final Velocity = Initial Velocity + (Acceleration × Time) → v = u + at
  2. Displacement = (Initial Velocity × Time) + ½ × (Acceleration × Time)² → s = ut + ½at²
  3. Final Velocity² = Initial Velocity² + 2 × (Acceleration × Displacement) → v² = u² + 2as

Force (N) = Mass (kg) × Acceleration (m/s²) → F = ma

Momentum (kg m/s) = Mass (kg) × Velocity (m/s) → p = mv

Change in Momentum (kg m/s) = Force (N) × Change in Time (s) → m∆v = F∆t

Wave Properties and Formulas

Wave Characteristics

  • Wavelength (λ): Distance from peak to peak (or trough to trough).
  • Amplitude: Maximum displacement from the equilibrium position.
  • Frequency (Hz): Number of wavelengths passing a point per second.

Period (s) = 1 / Frequency (Hz) → T = 1 / f

Wave Speed (m/s) = Wavelength (m) × Frequency (Hz) → v = fλ

Magnetism Principles

  • Magnetic Fields: Flow from North (N) to South (S) poles.
  • Right-Hand Thumb Rule: Determines the direction of the magnetic field around a current-carrying wire.
  • Fleming’s Left-Hand Rule:
    • Thumb: Resultant Force
    • Forefinger: Magnetic Field Direction
    • Middle Finger: Current Direction