On 4/02/2011 9:21 AM, Moike wrote:
Geoff Lock wrote:
OK, please bear with me as I lead up to how I got onto my torts on
physics in cycling.

Disclaimer.... I am a Physics teacher, (or will be in a couple of days)
but cycling is not on the VCE Physics curriculum

Heheheh!! I can almost see future Victorian students taking up cycling
and they don't know why ))

You are right about cycling on the flat. The additional mass means you
need to exert additional force to overcome inertia and accelerate from
rest, but (assuming it doesn't affect your wind resistance) once up to
speed it should make no difference. When coasting and slowing down the
slight increase in kinetic energy due to the increased mass should see
you roll a little further.

Hm, ok, that is kind of verifying my torts about my rolling momentum.

There would be lottle or no downhill effect, since the additional force
of gravity on your increased mass would be accounted for by the
additional force needed to accelerate the mass. (there would be a very
small increase in speed due to the fact hat while all the other forces
are greater, wind resistance is unchanged.)

I didn't have that many downhill sections but the couple I had seemed to
feel easier but I am guessing it may be simply psychological.

On uphill sections, the additional weight means you need to exert
greater force to climb the hill. As you point out, the additional weight
allows you to exert a higher down force on the pedals, but you still
need to use more energy to climb the hill.

It didn't seem to feel like I need to use a lot more energy than I
expected. Changing my riding style from seated to standing did seem to
increase power.

So yes, overall you should be slower, depending on how many hills you
climb, but perhaps your awareness of the extra load made you work a
little harder.

Dunno. Maybe you are right in that I was working a bit harder without
realising it. The brain is a weird thing - or maybe it's just me that's
weird and not me brain

Also, maybe the slight increase of 8kgs is not enough to stress my body
to the stage where degradation in performance is noticeable. So instead
of matters of physics, I should be talking about physiology(?). For
example, how would my body react if I loaded it up with an additional
80kgs (assuming I could, somehow, carry 80kgs snugly lashed on).

Damn, I wish there was a device which could measure the exact amt of
energy I burn given exact loads, frictional forces, wind, blah blah blah
Of cos, I would expect to pay no more than $35 off Ebay