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Island Physics

rotational mechanics

Hurricane Irma from space (September 2017)
Home >> AP Physics I >> Rotational Mechanics >> Rotational Energy
next topic >>

7.5 - Rotational Kinetic Energy

  • To understand that a rotating object has kinetic energy as work needs to be done to stop it.
  • To be able to calculate the rotational kinetic energy of a rotating object.
  • To be able to use the concept of rotational kinetic energy and the conservation of energy in the context of objects rolling down a slope.
Rotational Kinetic Energy
Rotating bodies are moving and therefore will require work to be done to stop them.  So they have kinetic energy.  The equation for this rotational energy is similar to the linear version:
\[KE_{linear} = \frac{1}{2}mv^{2}\]
​\[KE_{rotational} = \frac{1}{2}I\omega ^{2}\]
​When an object is rolling along the ground, it has two forms of kinetic energy- the linear KE of normal motion and the kinetic energy of the rotation. This becomes really important when we have objects rolling down hills!
Applying the conservation of energy:
\[​PE = KE_{linear}+KE_{rotational}\]
​When an object rolls down a slope some of the gravitational potential energy is transferred into rotational energy instead of just purely into linear kinetic energy.  The object moves slower.  The higher the rotational inertia of the object, the slower it moves down the hill.

Hurricanes Maria and Irma 2017 - This video shows how a hurricane has both linear motion (KE-linear) and rotational motion (KE-rotational).  This is just as they both swept through the Caribbean as category 5 storms.

Revision Sheets

Rotational Mechanics I - Wheel and Axle
Rotational Mechanics II - Rolling Down De Hill

Other Resources

https://www.geogebra.org/m/XMz9xCGC#material/Stu7gKyg
CK12 - Rotational Mechanics Questions
CK12 - Rotational Inertia
CK12 - Angular Momentum
Bike Speed and Rotation  - excellent paper written by a University of Washington professor


CK12 - Rotational Kinematics
CK12 - Rolling Energy Problems
YouTube clip - rigid body rotation lecture
Lady bug simulation
Picture
The Maine Ice Disk - January 2019
  • HOME
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    • Solids, Liquids and Gases
    • Waves
    • Astrophysics
    • Electricity
    • Magnetism
    • Nuclear Physics
    • IGCSE revision
  • Physics I
    • Kinematics >
      • Variables and Units
      • Describing Motion
      • Equations of Motion
      • Problem Solving
      • Projectiles
      • Kinematics Animations
    • Dynamics >
      • Forces
      • Static Equilibrium
      • Newton's Laws
      • Friction
      • Advanced Problems
    • Gravitation and Orbits >
      • Circular Motion
      • Vertical Circles
      • Universal Gravitation
      • Orbits
      • Circular Motion Animation
    • Energy >
      • Work
      • Springs
      • PE and KE
      • Conservation of Energy
      • Work-Energy Theorem
    • Linear Momentum >
      • Impulse
      • Conservation of Momentum
      • Types of Collision
      • 2-D Collisions
    • Simple Harmonic Motion >
      • Mass on Spring
      • Pendulums
      • SHM Animations
    • Rotational Mechanics >
      • Torque
      • Rotational Kinematics
      • Rotational Dynamics
      • Angular Momentum
      • Rotational Energy
    • Mechanical Waves >
      • Waves on a String
      • Sound
    • AP-1 Revision
    • AP Physics C (Mechanics)
  • Physics II
    • Fluid Mechanics
    • Thermal Physics
    • Electrostatics
    • Magnetic Fields >
      • EM Induction
    • Interference and Diffraction
    • Optics
    • Modern Physics
    • AP 2 Revision
  • OCEANOGRAPHY
    • The World Ocean >
      • What is Oceanography
      • History
      • Lat and Long
      • Size and Origin
      • Plate Tectonics
    • Seawater >
      • A Salty Sea
      • Measuring Salinity
      • Thermal Properties
      • Density Profiles
      • Drinking Seawater
    • Circulation and Climate >
      • Global Heating
      • Coriolis Effect
      • Surface Currents
      • Vertical Motion
      • Thermohaline Circulation
      • El Nino
      • Carbon Cycle
    • Waves and Tides >
      • Wave Motion
      • Formation of Waves
      • Beaches
      • Tsunamis
      • Tides
    • Observation Systems >
      • Challenges
      • The CTD
      • Moorings
      • Sound Waves
      • Robotics
      • Satellites
    • Weather and Navigation >
      • Weather Systems
      • Weather Forecasting
      • Hurricanes
      • Navigation
      • Life at Sea
    • Oceans and Mankind >
      • Ocean Acidification
      • Pollution
      • Fish Stocks
      • Climate Change
      • Energy Resources
    • Atlantic Explorer Cruise
    • ROVs
  • COLLEGE
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