Questions tagged [physics]
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46 questions
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How did we get to traditional size pulleys and when exactly did they become a relic of tradition?
Over time in the development of rear derailleurs brought to market, we can see most of the players going larger in tooth count most of the time, for both mainstream off-the-shelf components and also ...
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Do ALL non-instantaneous deceleration events transfer weight to front wheel?
There's a great question and discussion on hub vs disc brakes here. That got me wondering this: do ALL non-instantaneous deceleration events transfer weight to front wheel?
I've got a follow up ...
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When does the braking power stop scaling with Rotor Size
It's commonly established that the braking power scales with rotor size, and an optimal braking technique is to provide enough force for the rear wheel just to lift up. However, my question is wouldn'...
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Why do front gears become harder when the cassette becomes larger but opposite for the rear ones?
I noticed on mine and other road bikes that the "big" front gear becomes "harder" (more distance per revolution) when it switches to the bigger cassette. That makes sense, larger ...
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Infeasibility of a mechanical wind-up spring KERS (Kinetic Energy Recovery System) for bicycles
I'm curious about an explanation for why a wind-up spring KERS (Kinetic Energy Recovery System) isn't worth it for a bicycle.
The system I have in mind is instead of braking the rear wheel you engage ...
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Holding all other things constant, what is the performance difference of adding a pound of weight to each pedal on a bicycle?
I am looking for an answer that may include watts and/or calories per hour only. Please do not discuss wheels, tires, bearings, body weight, frame weight. Just help me understand the physics of adding ...
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storage pulley rack for a diagonal ceiling
i want a system based on a ceiling pulley for a quite heavy bike, the storage room is under the roof, so the ceiling (cement concrete material) is not flat.
Do the ceiling racks work well?
What about ...
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Momentum and gyroscopic difference between wheel sizes
A common folk wisdom in mountain biking is that smaller wheels (like 26") are "quicker" or "more flickable" and "better for courses that require lots of speeding up and ...
- 3,456
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How does biking speed correlate with the required effort?
The simple answer is that the faster you go the more effort/energy it takes but I would like to understand this in more detail, especially at relatively low speeds. Assume a flat smooth road and fix ...
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Would a heavy fork cause problem when climbing?
I have a MTB which has a 1.600g frame and 2.600g suspension fork. Does being heavy at the front cause a disadvantage when climbing?
- 2,168
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Healthiest bike posture for slower long rides
I'm looking for some evidence on bike posture and overall best positioning for healthiest rides that might be "long" (say around 30km) but also where speed is not a concern - think of ...
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How fast can a cyclist accelerate from a standing start?
I'm less interested in the empirical answer to this question and more interested in the theoretical physical dynamics that govern this.
I understand that the rider applies some force to the pedals (...
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Minimum speed when riding rollers
I have a set of rollers and a single-speed road bike. My 80-90 rpm speed is 27-30 kph (17-19 mph). I feel like I would be more stable with higher rpm, but it's harder to sustain.
If I understand this, ...
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Understanding science of speed difference between two bikes
I have two MTBs and one is slower than the other.
Bike1 has Deore derailleurs and a double chainring with 10 sprockets and Shimano hubs. Which has a great speed irrespective of the gear combination.
...
- 11
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Counter-intuitive steering in crosswinds with hands off the bars
It should not be surprising that it is difficult to ride in a straight line with both hands off the handlebars when there is a crosswind.
However, I find it most unintuitive, that for example if ...
- 170
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CdA of a bike without rider
This question at aviation.se got me calculating the acceleration of a bike strapped to the outside of a plane if the straps broke. As you do. I couldn't find a figure for CdA of a bike without rider ...
- 62.4k
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Is a bicycle wheel an indeterminate structure? [closed]
Does anyone knows whether a bicycle wheel is a statically determinate or indeterminate structure?
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Why does shifting under power affect shift quality?
I recently was attempting to shift up a hill and observed that
The shifting levers on the handlebars displayed significant resistance to my pushing them.
Despite several rotations of the crank, the ...
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Why are emergency inflation cartridges filled with CO2?
Why aren't they filled with ambient air using air compressors? Isn't compressing ambient air cheaper than generating CO2? If it is, then those cartridges would have two benefits:
Cheaper to ...
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Does changing gear relation produce different speed at same applied power?
When you are starting the ride, I potentially believe ("know?") that with a smaller plate(cog with fewer teeth in the rear cassette), you obtain more velocity than with a bigger plate(cog with more ...
- 113
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Maximum Descending Speed
This is a hypothetical question but I'm curious. Assuming an endless, freshly paved road with no turns, what would be my maximum speed?
EDIT
My question is too general so to help I'm adding some ...
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How much does wind affect the speed of a professional cycling peloton?
It's a well known fact that due to air resistance increase of speed on a bike takes non linear increase of power, so the huge marginal increase of power needed to go faster while riding at around 40-...
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Factors Involved With Tire Wobble When Riding Without Hands
I recently upgraded road bikes from a heavy one (25lbs+, 25mm) with thick tires to a very light one with skinny tires ( 16 lbs, 22mm ).
One thing that changed noticeably was the loss of the ability ...
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Does a fat tire ride softer than a skinny one at the same pressure?
Fat tires are associated with good bump absorption. Is this due to their fatness, or is it due to the low pressure with which they can be used?
If I pump a fatbike tire to 120 psi (yes, that would be ...
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Why do deep section front wheels get pushed around in crosswinds?
If a bike with a deep front wheel or a front diskwheel were to receive crosswinds with a 90 degree yaw angle handling would not be affected since the pressure would be equally distributed among the ...
- 1,468
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Dynamic stability of a tricycle
I'm currently designing the "electric bike of my dream" (please do not laugh! it's for fun, nothing serious), and I came up after some though with a tricycle, where 2 rear wheels are supporting the ...
- 456
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Loading front wheel in a sharp turn?
When turning sharp at high speed, does it make sense to shift the weight to reduce risk of skidding?
I do not see the point of doing so. Both wheels are leaned at the same angle against the ground no ...
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Does it takes longer to cycle a route with a mountain on it comparing to the same distance without a mountain? What is the cause of that? [duplicate]
Imagine you cycle 100km. On one route there is a mountain 100meter high on an other route is not a mountain but a straight way.
Usually it takes longer on the route wiht a mountain. One reason for ...
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Where does the energy loss in cycling go proportionally? [duplicate]
If you are biking on level ground with no wind, I understand that there are losses inherent in your activity which you provide effort to overcome (if you want to maintain a steady speed):
Air/wind ...
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Is contact patch area governed by A=W/P
contact_patch_area = weight / tire_pressure
Is this true?
Wikipedia says "mostly".
This guy analyzed some automobile tire manufacturer, and although the info was self-conflicting, he concludes ...
- 14k
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Riding into a headwind faster than my top speed - how is it possible?
Recently we've had some pretty strong winds here -- today the weather forecast said 20mph gusting to 30mph, but a few weeks ago the gusts were supposedly over 40mph. The forecast direction was within ...
- 62.4k
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Why do skinny tires require less pedal effort?
Everyone knows (citation needed) that (at fixed rim diameter) tyres with smaller section require less effort to move around (at least on a paved road).
TL; DR.
Why?
A bit of context.
I always ...
- 496
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Descending without braking: where's the sweet spot?
This may get too math-heavy, but it seems that only a few variables are needed to estimate the optimum slope to descend without gaining/losing speed.
I looked around, but wasn't able to find anything ...
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(racer) Standard vs compact crankset: Increased leverage for same gear ratios true?
I'm a road and mtb regional racer about to have a go at my first road endurance nationals very soon.
I'd like some educated scientifically validated answer on a matter that has been on my mind ever ...
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why does the lemond revolution turbo trainer quote its volume of air resistance in meter^2 and not per second cubed?
The Lemond revolution states that it creates consistent aero resistance with its fan power from 0 newtons to 40 newtons along one axis and 0 to 160 meters/second^2 on the other axis. Since air flow is ...
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If I attached a "pointy" pool noodle to my bike, would it make me safer even from sadistic drivers?
A few sources suggest that mounting a foam pool noodle on the back of your bike can help stop drivers from passing too closely. Such noodles are available at my dollar store, unlike spring-loaded bike ...
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Is a bike faster than a car for the first ten metres? [closed]
The city I live in has just installed cycle boxes in front of traffic at light controlled intersections. This has spark a lot of debate online.
My experience is that I will generally, through timing ...
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Approximately where is the center of mass of a mountain bike?
Take a "standard" multipurpose bike like this one: http://www.islabikes.co.uk/bike_pages/beinn29.html (Weighing 12.2kg)
I'm conducting a physics investigation, and for this I need to know the ...
- 603
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Is it possible to estimate road grade while riding?
It would be nice to be able to estimate the grade of a road while riding, even if the estimate is not completely accurate. With a GPS, in theory it should be possible in theory to ride a short ...
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Does a 700c wheel help you go faster?
Someone suggested going with a 700c wheel to go faster, and after thinking about it I am wondering if a larger wheel actually does go faster. I understand that your gears will cause a wheel to rotate ...
- 3,115
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What does a cyclocomputer actually measure for calculating the speed of the bike?
What does a cyclocomputer actually measure for calculating the speed of the bike?
Is it the time for one revolution $T$ or is it the number of revolutions $n$ per given time $t_0$?
If the radius of ...
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How does a bike absorb all the energy in landing from a big drop?
There are countless videos showing BMX/freeride/downhill etc. riders jumping and dropping from heights. For the unprofessional spectator, they seem impossible to survive.
From the physical point of ...
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How do I calculate the power required to climb a hill at a given cadence?
Suppose I ride at a cadence of 50RPM for 10 minutes with a 39x23 gear ratio on a hill with 10% grade. Is there a simple formula to calculate the power output required?
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What is the effect of adding weight to a wheel vs adding it to the frame?
There are claims often made that, eg, "An ounce of weight at the rims is like adding 7 ounces of frame weight." This is "common knowledge", but a few of us are skeptical, and our crude attempts at ...
- 54k
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What bicycle design factors affect stopping power?
I've been under the impression that bikes and motorcycles cannot stop as quickly as cars. I'm curious what factors have the largest impact on bike stopping distance.
What comes to my mind are:
Tire ...
- 2,569
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What makes a bike stay upright when moving?
What makes a bike stay upright when it is in motion? What is the relationship between speed and stability? Is it a linear relationship?
I could ask this on the physics site however I am hoping ...
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