why is a running wheel stable?

unbiased

Senior member
Nov 17, 2002
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Hey! don't say 'go and look into physics text book'. I knew the answer to this but have forgotten and I don't have any text books at hand. So please write a few lines to help me recollect the reason. I remember it has got something to do with shifting of the centre of gravity.
 

glugglug

Diamond Member
Jun 9, 2002
5,340
1
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Tilting a wheel perpendicular to the direction of spin would change the direction of angular momentum of the wheel, thereby requiring higher torque than if the wheel wasn't spinning, to account for that momentum change.
 

Valkerie

Banned
May 28, 2005
1,148
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when it accelerates, assuming that the wheel is architecturally constructed properly, it will only go in the direction it's momentum can offer, thus it will rotate in a sequencial manner. it's nature will be to continue until momentum slow*s it down with friction, whether it be air or any type of surface or gears.
 

Heisenberg

Lifer
Dec 21, 2001
10,621
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Originally posted by: glugglug
Tilting a wheel perpendicular to the direction of spin would change the direction of angular momentum of the wheel, thereby requiring higher torque than if the wheel wasn't spinning, to account for that momentum change.
*ding ding ding*

It's the same idea (i.e. Newton's Second Law) as to why you have to apply a force to change the momentum of a mass. Torque is simply the rotational analogue of force, and angular momentum that of linear momentum. The part that is most often confusing is that the direction of the angular momentum is orthogonal to the direction the wheel spins.
 

TuxDave

Lifer
Oct 8, 2002
10,571
3
71
Originally posted by: Heisenberg
Originally posted by: glugglug
Tilting a wheel perpendicular to the direction of spin would change the direction of angular momentum of the wheel, thereby requiring higher torque than if the wheel wasn't spinning, to account for that momentum change.
*ding ding ding*

It's the same idea (i.e. Newton's Second Law) as to why you have to apply a force to change the momentum of a mass. Torque is simply the rotational analogue of force, and angular momentum that of linear momentum. The part that is most often confusing is that the direction of the angular momentum is orthogonal to the direction the wheel spins.

Right hand rule! :)