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Jenny
21483.  Fri Jun 10, 2005 8:32 pm Reply with quote

Quote:

women confuse me.


That's as it should be...

Has anybody mentioned programming the video yet?

 
Natalie
21489.  Sat Jun 11, 2005 9:23 am Reply with quote

Chemistry confuses me. Also, women drivers who despise women drivers do too.

 
Flash
21490.  Sat Jun 11, 2005 9:42 am Reply with quote

Bicycles - because they seem to be a free lunch in that you go further and faster whilst expending less energy. How does that work, then?

Also, how come the faster they go the stabler they get?

 
Beehive
21492.  Sat Jun 11, 2005 10:16 am Reply with quote

Flash wrote:
Bicycles - because they seem to be a free lunch in that you go further and faster whilst expending less energy. How does that work, then?


I thought that was the point of all machines?
A lever for example- you can lift more while expending less energy. I don't know how it works, but it must be fairly simple.

 
Flash
21494.  Sat Jun 11, 2005 10:33 am Reply with quote

OK then, levers too.

 
Caradoc
21519.  Sun Jun 12, 2005 6:56 pm Reply with quote

Flash wrote:
Bicycles - Also, how come the faster they go the stabler they get?


The wheels act as gyroscopes, as the bulk of their mass is at the rim they make fairly good ones, as with all gyroscopes the faster they rotate the harder it is to change their plane of rotation.

 
Flash
21522.  Sun Jun 12, 2005 8:09 pm Reply with quote

I wish it was that simple. For this:
Quote:
The above argument (about centrifugal force) fails to explain why a bicycle will remain upright for as much as 20 seconds or so if it is allowed to roll freely. It also fails to explain why a bike feels extremely stable when it is moving at very high speeds. Attempts to explain this stability through torque arguments (associated with the spin of the front wheel) by references 1-3 and 5 were refuted by D.E.H.Jones who actually built what he called an “unrideable-bicycle” by attaching a second wheel to the front of a bike whose purpose it was to cancel the torque created by the spinning of the first wheel. The problem with the unrideable bicycle was that it was quite rideable. Another possible reason for the stability of the bicycle follows from the equation of motion of the center of mass of a bike rider system (eq 5). If the lean angle of a bicycle is proportional to the steering angle, the equation of motion for the center of mass of the bike-rider pair reduces to the equations of motion for a damped simple harmonic oscillator. This could lead to yet another explanation for the stability of the bicycle.

and more, see http://www.wooster.edu/physics/JrIS/Files/Brad.pdf.

Also, this one:
Quote:
That gyroscopic effects are unimportant at normal cycling speeds was shown by physicist and researcher into bicycle stability David E. H. Jones, whose series of "URBs" ("unrideable bikes" with various modifications to the front end) included a bike which cancelled the gyroscopic effect of the front wheel by dint of attaching a second wheel to his front forks (alongside the regular wheel) whose lower edge was about an inch (25 mm) above the ground. By gearing this wheel to the regular front wheel so that it spun in the opposite direction at equal speed, the net angular momentum of both wheels together was close to zero. Jones found he could ride this bike with no difficulty, but did discover that without a rider the non-gyroscopic bike fell over much faster than a regular bike.

http://psychcentral.com/psypsych/Bicycle#Bicycle_physics

 
dr.bob
21551.  Mon Jun 13, 2005 7:57 am Reply with quote

Quote:
Jones found he could ride this bike with no difficulty, but did discover that without a rider the non-gyroscopic bike fell over much faster than a regular bike.


Surely that proves that the gyroscopic effect plays at least some part in the stability of the bicycle. Clearly the most important reason a bicycle stays upright is that the rider is compensating for any tilts and wobbles. Presumably this is easier to do when moving faster since you have to turn the wheel less to move the bicycle the same distance laterally in the same space of time compared to when you're cycling slowly.

As for things that cause confusion, I could never get my head around hyperbolic calculus, but perhaps that's just me.

 

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