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For a good view of all the demos please sit near the front (ie front 5 rows)

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  1. For a good viewof all the demosplease sit nearthe front(ie front 5 rows)

  2. BoomerangsBouncing Ballsandother spinning things Dr Hugh HuntCambridgeUniversityEngineeringDepartment Trinity College Cambridge

  3. Bouncing balls

  4. Spinning and Rolling the gyroscopic effect

  5. The Gyroscopic Effect • Coffee grinder • Angle grinder • Hair drier For details go to www.hughhunt.co.uk

  6. Circular motion force mass speed string

  7. 1: ballet dancers and ice skaters Moment of Inertia J : “an Angular Mass” Arms in, FeelLight J J w w SpinFAST Conservation of Angular Momentum J w Arms out, feelHeavy Spin slowly

  8. 2: pointing the Hubble Telescope   Still no spin ! No spin Conservation of Angular Momentum Jw

  9. 3: spinning in space     Conservation of Angular Momentum Jw

  10. The Gyroscopic effect C Precession C Couple W C w C SPIN (Angular momentum) C = J w W J = moment of inertia of wheel

  11. Air deflected downwards Air flow Lift force How Wings Work F V

  12. Boomerangs C Precession C Couple more lift faster Direction of travel Spin C slower less lift

  13. Physics of boomerangs 4J rCLpa4 where R = path radius J = moment of inertia r = air density CL = lift coefficient a = size of boomerang R = ________ andaw = 2 V flick-of-the-wrist w = boomerang spin V = boomerang velocity

  14. Boomerangs come in many shapes and sizes. They make great christmas presents!

  15. The End www.hughhunt.co.uk Google: Hugh Hunt Boomerangs Trinity College Cambridge www.trin.cam.ac.uk Cambridge University Engineering Dept www.eng.cam.ac.uk

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