Invisible schrieb:

> Random question: A gyroscope works because it is [apparently] impossible 
> to turn the axis of rotation of a rapidly spinning object. So how come 
> cars can go around corners?

Because that's actually /not/ why a gyroscope works :-)

The gyroscope works because angular momentum in a closed system must be 
constant. Angular momentum is a vector, and as long as the gyroscope is 
undisturbed, this vector is parallel to the axis of rotation.

What happens when you (comparatively slowly) rotate a rapidly spinning 
object's axis is that as the object's angular momentum vector changes, 
it will exert a torque force on its bearings that will impart this 
difference in angular momentum unto the "outside world". (As a matter of 
fact, this torque force does not even oppose the turning of the axis, 
but acts perpendicular to it instead.)

The trick with a gyroscope is that the suspension is designed in such a 
way that (a) the rapidly spinning object itself is subject to as few 
rotational movement as possible in the first place, and (b) that it 
cannot impart any angular momentum unto the "outside world". Instead, 
the torque force will just cause another turning of the gyroscope's 
axis, which again will result in a torque force, now countering the 
initial disturbance.


In contrast, when you steer a car around a corner, the resulting effect 
is that you just slightly change the angular momentum of the earth, to 
compensate for any rotating parts' (motor, wheels etc.) change in agular 
momentum.

You can experience the effects, however, when riding a bicycle "without 
hands": If you are going fast enough and lean sideways so that the bike 
will tilt, the front wheel will automatically turn in that direction 
(even though most front wheel suspensions are actually designed in such 
a way that gravitation alone would turn the wheel to the opposite side 
instead).

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