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Hugh Hunt, Trinity College, Cambridge www.hughhunt.co.uk
For a good viewof all the demosplease sit near
the front(ie front 5 rows)
Hugh Hunt, Trinity College, Cambridge www.hughhunt.co.uk
BoomerangsBouncing Balls
andother spinning things
Dr Hugh Hunt
CambridgeUniversity
EngineeringDepartmentTrinity College Cambridge
Hugh Hunt, Trinity College, Cambridge www.hughhunt.co.uk
Bouncing balls
Hugh Hunt, Trinity College, Cambridge www.hughhunt.co.uk
Hugh Hunt, Trinity College, Cambridge www.hughhunt.co.uk
Spinning and Rolling
the gyroscopic effect
Hugh Hunt, Trinity College, Cambridge www.hughhunt.co.uk
The Gyroscopic Effect- Coffee grinder- Angle grinder
- Hair drier
For details go to www.hughhunt.co.uk
Hugh Hunt, Trinity College, Cambridge www.hughhunt.co.uk
Hugh Hunt, Trinity College, Cambridge www.hughhunt.co.uk
Circular motion
speed
mass
force string
Hugh Hunt, Trinity College, Cambridge www.hughhunt.co.uk
Spin
FAST
Arms in,Feel Light
Spin
slowly
Arms out,
feel Heavy
1: ballet dancers and ice skatersMoment of Inertia J : “an Angular Mass”
Conservation of Angular Momentum J
JJ
Hugh Hunt, Trinity College, Cambridge www.hughhunt.co.uk
2: pointing the Hubble Telescope
No spin
Still no spin !
Conservation of Angular Momentum J
Hugh Hunt, Trinity College, Cambridge www.hughhunt.co.uk
3: spinning in space
Conservation of Angular Momentum J
Hugh Hunt, Trinity College, Cambridge www.hughhunt.co.uk
The Gyroscopic effect
Couple
C
SPIN
(Angular momentum)
C = J
Precession
J = moment of inertia of wheel
Hugh Hunt, Trinity College, Cambridge www.hughhunt.co.uk
How Wings Work
Air flowAir deflecteddownwards
V
Liftforce
F
Hugh Hunt, Trinity College, Cambridge www.hughhunt.co.uk
BoomerangsPrecession
Directio
n of travel
faster
slower
more lift
less lift
Couple
Spin
Hugh Hunt, Trinity College, Cambridge www.hughhunt.co.uk
Physics of boomerangs
4J
CLa4
where R = path radius
J = moment of inertia
= air density
CL = lift coefficient
a = size of boomerang
R = ________
flick-of-the-wrist
= boomerang spin
V = boomerang velocity
and a = 2 V
Hugh Hunt, Trinity College, Cambridge www.hughhunt.co.uk
They make great christmas presents!
Boomerangs come in many shapes and sizes.
Hugh Hunt, Trinity College, Cambridge www.hughhunt.co.uk
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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