• Bookmarks

    Bookmarks

  • Concepts

    Concepts

  • Activity

    Activity

  • Courses

    Courses

    Courses
    History Empty State Icon

    Your Courses

    Your courses will appear here.

    Log InSign up
Anylearn Logo
About
Guest User
Sign in to save progress
Sign InSign up

My Quests

🚀
All Quests Blend
AI-curated mix
+Add Quest

CUSTOMIZE YOUR LEARNING

Anylearn Logo
About
Guest User
Sign in to save progress
Sign InSign up

My Quests

🚀
All Quests Blend
AI-curated mix
+Add Quest

CUSTOMIZE YOUR LEARNING

⚙️

Rotational Friction

How torques from friction resist rotation and drain energy

Physics • Rotational Dynamics / Mechanics🚀 Beginner

Rotational friction describes the torques and resistive forces that oppose rotational motion, including bearing friction and rolling resistance. Learners will identify sources of rotational friction, calculate frictional torque, and evaluate its effect on rotational dynamics and energy loss.

⏱️
30 minTypical time
📋
4Prerequisites
🎯
3Learning outcomes

📋Prerequisites

  • Basic Newtonian mechanics
  • Concept of force and torque
  • Linear friction (static and kinetic)
  • Moment of inertia and angular motion

🎯What You'll Learn

  • ✓Explain sources of rotational friction (bearing, surface contact, viscous drag)
  • ✓Compute frictional torque for common configurations and predict deceleration
  • ✓Estimate energy dissipation from rotational friction and relate to efficiency

🔗Related Concepts

prerequisiteTorqueprerequisiteMoment of Inertiasimilar-toRolling Resistancebuilds-onAngular Momentumsimilar-toBearing Friction and Lubrication

🔑Key Formulas

  • τ_f = F_f × r (frictional torque = frictional force × lever arm)
  • F_f ≈ μ_r N (rolling/rotational friction approximated using effective coefficient μ_r and normal force N)
  • Energy loss per revolution ≈ τ_f × (2π) (work done by friction per turn)
  • Angular deceleration: α = τ_net / I (includes frictional torque in τ_net)

    • Common Experiments & Demonstrations

  • Rolling cylinder down an incline to compare rolling resistance vs. slipping
  • Rotating disk with adjustable brake to measure spin-down time and infer torque
  • Torque sensor on a shaft with different bearings or lubricants
  • Viscous drag demonstration using rotating vanes in fluids

    • Practical Applications

  • Wheel bearings and vehicle rolling resistance (fuel efficiency)
  • Brake systems and controlled rotational dissipation
  • Rotating machinery: motors, turbines, and gear trains
  • Precision instruments (gyroscopes, hard drives) where low rotational friction is critical

    • Typical Problems & Assessment Tips

  • Set up free-body/torque diagrams including frictional torques
  • Convert between force-based friction models and torque expressions
  • Estimate order-of-magnitude energy loss per unit time or per revolution
  • Recognize when to use rolling resistance coefficients vs. viscous/solid friction models

    • 🔗Learn More

    🎓Khan Academy — Rotational Dynamics🔗HyperPhysics — Rotational Motion (Georgia State Univ.)🔗MIT OpenCourseWare — Classical Mechanics (8.01)📖Wikipedia — Rotational Motion📖Wikipedia — Rolling Resistance🔗Engineering Toolbox — Friction Coefficients
    🌀

    Introduction to Rotational Friction

    Basic concept, why it matters, and the primary factors involved.

    ⏱️8 min

    SPEED READING MODE
    Complete!
    1 / 0
    250 WPM
    🖼️

    No images to display

    Factors Affecting Rotational Friction

    📐

    Physical Principles & Key Formulas

    Core physics and mathematical expressions used to model rotational friction.

    ⏱️18 min

    SPEED READING MODE
    Complete!
    1 / 0
    250 WPM

    Mathematical Formula

    Variables:

    Type: mathematical

    Derivation of Frictional Torque

    🔬

    Experiments & Real-World Examples

    Hands-on setups, observed behavior, and example systems where rotational friction is important.

    ⏱️22 min

    🧠

    Problem Solving & Practice

    Worked examples, common mistakes, and targeted practice problems to test understanding.

    ⏱️25 min

    SPEED READING MODE
    Complete!
    1 / 0
    250 WPM
    Multiple-Choice Quiz
    1/0
    ⚙️

    Applications, Advanced Topics & Resources

    Industrial applications, advanced models, simulations, and where to go next.

    ⏱️20 min

    SPEED READING MODE
    Complete!
    1 / 0
    250 WPM
    💬AI Expert Chat

    SPEED READING MODE
    Complete!
    1 / 0
    250 WPM
    🎥Research Interview: Rotational Friction in Practice