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Although the *forces* of gravity and centrifugal force don't balance, their
*torques* do (i.e., about the pivot point where tire meets road). Although
that idea would be easy to explain (even to someone who hasn't heard of
angular momentum), in this case I think most people would regard the
distinction between force and torque as a detail of little importance. So
I would suggest that it would be more important to focus on the other
factors in a letter.
QUESTION: Should I even bother to respond to the article since the "common
sense" (which isn't common) of the vast majority of the readers will agree
that outward centrifugal force balances gravity and they will never have
heard of angular momentum?
Then he adds,
A SECOND INTERESTING ASIDE: If you do not ride a motorcyle, you can
demonstrate counter-steering to yourself while riding a bicycle.
I don't know the first thing about motorcycles, but I know for sure thatAgain quoting me:
*during* a turn on my bicycle, the handle bars are car-steered. I assume
that the same is true of motorcycles, and that counter-steering applies to
*starting* a turn?
While
riding at a safe, reasonable speed, gently push forward on one of the
handgrips and notice what happens to the bicycle.
....
Re-performing the experiment confirmed my previously formed opinion based
just the sort of thing you mentioned above. My explanation is somewhat
different than yours.
Pushing on the right handle bar causes the bicycle to turn left just as a
car does; there is no counter-steering effect directly attributable to the
push on the handle-bars. However, the bicycle is now turning while
vertical: in the bicycle's reference frame, there is a torque from
centrifugal force tending to tip the bicycle over to the right, and no
torque due to gravity. If this condition persisted, the bicycle would
indeed fall over to the right - ouch!
there is no counter-steering effect directly attributable to the
push on the handle-bars.
in the bicycle's reference frame, there is a torque from
centrifugal force tending to tip the bicycle over to the right, and no
torque due to gravity. If this condition persisted, the bicycle would
indeed fall over to the right - ouch!
If this condition persisted, the bicycle would
indeed fall over to the right - ouch!
To summarize, the initial counter-steer is just a way to tip the bike to
the right, so that a balanced turn can then follow.
To summarize the differences from David's understanding, the torque on the
front wheel (about the steering column) from the initial counter-steer is
not the main cause of the bike tilting - instead the tilt is due to
centrifugal force.