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Understanding Flywheel Rotation Dynamics

Apr 5, 2025

Rotation of a Flywheel

Introduction

  • Flywheel: A spinning disk, rotating counterclockwise.
  • Starts from rest and rotates an angle of 65 radians in 15 seconds.
  • Objective: Determine average angular speed, direction of angular speed, and tangential speed at different points.

Average Angular Speed

  • Initial Conditions:
    • Starts from rest (initial angular speed = 0).
    • Rotational angle = 65 radians.
    • Time taken = 15 seconds.
  • Formula: Average angular speed = Change in angle / Change in time.
    • Analogous to average linear speed: Change in distance / Change in time.
    • Here, distance is equivalent to rotational angle (theta).
  • Calculation:
    • Final angle = 65 radians, Initial angle = 0.
    • Final time = 15 seconds, Initial time = 0.
    • Average angular speed = 65 radians / 15 seconds = 4.33 radians/sec.

Direction of Angular Speed

  • Right-Hand Thumb/Curl Rule:
    • Curl fingers in direction of rotation.
    • Thumb points in direction of angular velocity.
  • Result:
    • For counterclockwise rotation, thumb points upwards, indicating angular speed is vertically upward.

Tangential Speed

  • Definitions:
    • Tangential speed: Speed at a specific location, direction is tangent to the point.
    • Formula: Tangential speed = Radius x Angular speed (v = r * ω).
  • Characteristics:
    • Angular speed (ω) is constant across all points of the flywheel.
    • Tangential speed varies with radius; greater radius = greater tangential speed.
  • Example Calculations:
    • At 5 cm from the center (converted to meters), tangential speed = (0.05 m) x (4.33 rad/sec) = 0.2165 m/sec.
    • Larger radius will yield a higher tangential speed.
  • Key Points:
    • Angular velocity is not dependent on position.
    • Tangential speed is position-dependent, increasing with radius.*

Conclusion

  • Summary: Explained rotation dynamics of a flywheel including average angular speed, direction of angular velocity, and position-dependent tangential speed.
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