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Angular Momentum & Moment of Inertia Calculator

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### Physics & Classical Mechanics: Conservation of Angular Momentum 1. **The Law of Conservation of Angular Momentum**: In the absence of an external net torque, total angular momentum remains.

Reviewed by Ahmad Faraz · BSCS
Last updated:
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📊 Results

Angular Momentum & Energy Summary
Angular Momentum (L): 235.62 J·s (235.62 kg·m²/s) ➔ Inertia (I): 1.8750 kg·m² | Energy: 14.80 kJ (14,804 J) | ω: 125.7 rad/s (1200 RPM) | Rim Speed: 62.8 m/s
Angular Momentum (L in kg·m² / s or J·s)
235.619 kg·m² / s (J·s)
Mass Moment of Inertia (I in kg·m²)
1.8750 kg·m² (Moment of Inertia I)
Rotational Kinetic Energy (E_rot in Joules & kJ)
14.804 kJ (14,804 Joules Stored Energy)
Angular Velocity (ω in rad / s)
125.66 rad / s (1200 RPM)
Tangential Rim Velocity (v_tan in m / s & km / h)
62.83 m / s (226.2 km / h Tangential Velocity)
✦ Classical Mechanics & Rotational Dynamics Diagnostic
Classical Rotational Mechanics Model (L = I·ω | 15 kg SOLID CYLINDER DISK | r = 0.5m @ 125.66 rad/s [1200 RPM]): [1. Angular Momentum & Conservation]: The rotating body possesses **235.619 kg·m²/s (J·s) of angular momentum** (a conserved vector quantity in isolated systems). [2. Mass Moment of Inertia]: The rotational inertia is **I = 1.8750 kg·m²**, representing resistance to angular acceleration. [3. Stored Kinetic Energy]: Stores **14.804 Kilojoules (14,804 Joules) of rotational kinetic energy**, with an outer perimeter tangential rim velocity of **62.83 m/s (226.2 km/h)**.
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📐 Formula

Rotational Dynamics & Angular Momentum equations:
Angular Momentum: L = I × (kg×m^2/s or J×s)
Solid Cylinder Inertia: I = (1 ÷ 2) m r^2, Solid Sphere: I = (2 ÷ 5) m r^2, Point Mass: I = m r^2
Angular Velocity: = 2 × RPM60 (rad/s)
Rotational Kinetic Energy: E_rot = (1 ÷ 2) I ^2 (Joules)
Tangential Rim Velocity: v_tan = × r (m/s)

💡 Practical Example

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For example, evaluating a \(15.0\text{ kg solid steel flywheel disk}\) with radius \ spinning at \(1,200\text{ RPM}\)): Moment of inertia is \(0.5)^2 = \mathbf{1.875\text{ kg}\cdot\text{m}^2}\). Angular Momentum is \}}\), storing \(\mathbf{14.80\text{ kJ (14,804 Joules)}}\) of rotational energy with an outer rim speed of \}\).

📖 About Angular Momentum & Moment of Inertia Calculator

Physics & Classical Mechanics: Conservation of Angular Momentum

  • The Law of Conservation of Angular Momentum: In the absence of an external net torque, total angular momentum remains strictly constant: .
  • The Figure Skater Effect: When an ice skater pulls their arms inward, their radius r decreases, slashing their moment of inertia I; to conserve L, their angular spin speed ω accelerates dramatically.

How to Use This Calculator

Enter your Rotating Body Geometry — choose from Solid Cylinder / Disk / Flywheel (I = 1/2 m r²), Point Mass / Orbiting Particle (I = m r²), Solid Sphere / Planet (I = 2/5 m r²), Object Mass (m [kg]) (e.g. 15 (15 kg flywheel / satellite)), Radius or Length (r [Meters]) (e.g. 0.5 (0.5 meters = 50 cm)), Rotational Velocity Input Unit — choose from Revolutions Per Minute (RPM), Radians per Second (rad / s), and Rotational Speed (RPM or rad / s) (e.g. 1200 (1,200 RPM)). Verify your units match the formula standard (SI vs imperial) before entering values.

The Formula

Rotational Dynamics \& Angular Momentum equations:

Angular Momentum: L = I × ω (kg·m^2/s or J·s)

Solid Cylinder Inertia: I = (1) / (2) m r^2, Solid Sphere: I = (2) / (5) m r^2, Point Mass: I = m r^2

Angular Velocity: ω = (2 π × RPM) / (60) (rad/s)

Rotational Kinetic Energy: E_rot = (1) / (2) I ω^2 (Joules)

Tangential Rim Velocity: v_tan = ω × r (m/s)

Worked Example

For example, evaluating a 15.0 kg solid steel flywheel disk with radius \ spinning at 1,200 RPM): Moment of inertia is 0.5)^2 = 1.875 kg·m^

  • Angular Momentum is \, storing 14.80 kJ (14,804 Joules) of rotational energy with an outer rim speed of \.

Understanding Your Result

Scientific calculations require careful attention to significant figures and units. Your result is only as precise as your least precise input — expressing the result with more significant figures than the inputs implies false precision. For laboratory or regulatory work, verify which measurement standard applies (SI, ASTM, ISO) and whether temperature, pressure, or concentration conditions affect the formula. Cross-reference results against published reference values for your specific material or compound.

💡 Methodological Standards & Calculation Accuracy

  • All calculations are performed client-side in your browser using verified, standards-compliant mathematical algorithms.
  • Results are provided for educational and informational analysis; verify critical applications with certified domain specialists.
  • Ensure input values are entered in consistent units matching the selector options to guarantee accurate outputs.
  • Periodic recalibration is recommended whenever baseline assumptions, operating parameters, or external conditions change.

Results are for informational and educational purposes only. Always verify critical decisions with a qualified professional.

❓ Frequently Asked Questions

What is the formula for angular momentum?

Angular Momentum (L) = Moment of Inertia (I) × Angular Velocity (ω), or L = mvr for an orbiting point mass.

What are the standard units of angular momentum?

The SI unit of angular momentum is kilogram meter squared per second, which is dimensionally equivalent to Joule-seconds (J·s).

What is the moment of inertia for a solid disk or flywheel?

For a uniform solid cylinder or disk rotating around its central axis, Moment of Inertia I = 1/2 × m × r².

How do you calculate rotational kinetic energy?

Rotational Kinetic Energy (E_rot) = 1/2 × I × ω² (in Joules).

Why is angular momentum a vector quantity?

Angular momentum has both magnitude and directional orientation governed by the Right-Hand Rule along the axis of rotation, creating gyroscopic stability (e.g. why spinning tops and bicycles remain upright).

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