The Physics of Cycling!
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- Опубликовано: 9 июл 2024
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This channels videos are so informative and well-made. Way better than a lot of the other channels because it breaks down and explains the topic so well. Good job👍🏻
As a bmx rider that uses flats, we also pull up using our hamstrings, we push our feet into the pedals, then hook our toes around the pedal, the pull up, so it's not limited to just clips.
ok. Fair enough. Never really thought about that technique. Good catch.
@@sportology1 it's an example of friction so I figured that I'd chime in here. Also not too many people do it so I see why you didn't talk about it.
Cool, but I would've thrown in a remark about how much each extra spoke costs you in wind resistance. Your Bontragers are looking good in that department.👍 As far as I can tell they're identical to mine.
Btw, I notice you wrote your script really, really well.👍
Fantastic explanations, thank you!
The kinetic energy of the wheels is extremely low compared to the whole system, so there is no reason to to optimize the weight of the wheels, one should rather optimize the aerodynamics of the wheels. In most cases, more aero wheels accelerate faster than lighter wheels
Pls a video about sternum pain while doing push ups !!
this video is very informative! i understood everything. in a way, it can help choose what kinda bike should i get
Very informative and quality information
Please make a video of shin splints !
Can you speak to the diffence between how fighting gravity while climbing vs. not having to fight it while riding flats?
Well having ridden bikes 20+ years, including multiple tours I'll try to explain some of the key differences:
- Wind or air resistance increases with the square of velocity while the resistance from climbing increases linearly with the gradient. So riding up twice the gradient is roughly twice as hard, while riding twice the speed is closer to 4x as hard. So at first glance this seems to make hills look better, but here's the catch: Usually when you ride up, you want to ride down the other side. The way up will be slow, the way down fast. But a high speed saves less time than a slow section costs you. If your ride is made up of two sections of 10 km and you ride 10 km/h on the first half and 30 km/h on the second it will take you 1 hour + 20 minutes = 80 minutes. But if you ride a steady 20 km/h for the whole ride it only takes you 60 minutes. In fact since the first half at 10 km/h takes you the same time as the whole trip at a steady 20 km/h you cannot beat that time, no matter how fast you are on the second leg. But remember, higher speeds become exponentially harder. So the energy you gained by riding up will help you be faster on the way down, but the increase in air resistance is so great, that it won't ever compensate for the time lost ascending. That's the main reason why hills slow you down. Constant intensity at constant speed is best, that only works in flats.
- One of the greatest limitations to constant movement isn't actually strength or oxygen, but heat management. That's why humans are actually pretty much the best animal on earth for ultra long distances, even on foot. A cheetah leaves even peak form Usain Bolt in the dust. But that's for a sprint. After a while its fur causes it to overheat and it has to slow down or it will suffer a heat stroke. Our lack of fur combined with sweat glands nearly everywhere allow us to keep going, as long as we get sufficient food and water. On a bicycle this is also key. I did a tour last summer where temperatures rose to 38°C and the sun was shinning intensely. For some days I drank over 10 litres of fluid in a day, without excessively having to go to the toilet. But I didn't feel sweaty. The air wasn't too humid and with the air flowing past me at speed, the sweat evaporated nicely, keeping me cool. In fact I find it more comfortable to cycle at a moderate pace during summer heat than standing still outside. But this only works if you move through air with some speed. That doesn't work going up hills. You still have to put force into your pedals, but you're much slower. So you will feel the sweat accumulating and body temperature rising. So putting the same force into your pedals feels like a bigger effort. That's why I avoid hills during the hottest parts of the day in summer. Always do them in the morning if you can.
- If you ride up a hill, your bike naturally wants to roll down. Ignoring breaks (only useful when at a standstill) you'll have to constantly fight this force wanting to pull you down. When walking up a hill it's easy to just stand. If it gets steep, just slow down. On a bike that's less true, plus balance becomes an issue at low speed. So if it's too steep, walking becomes more efficient (ever see someone climb up a wall on a bicylce?;) ). While bicycles are much more efficient in flat terrain, after a certain gradient, that stops being the case. I'm not sure on the exact numbers, I'd guess it's somewhere around 8-10° gradient, but might be even earlier.
- One of the main reasons why cycling is efficient are modern gears (derailleur or hubs). These gears allow us to keep pedaling at the most efficient intensity, even if the terrain or wind changes. Because our muscles are not perfectly linear in how efficiently they can create a force. Imagine any exercise with weights, I'll take a bench press as an example: There is a weight near the maximum you can manage. You might be able to do three repetitions with this weight. But how many could you do with half the weight? You could likely do 25+ repetitions quite easily. So by reducing the load on our muscle we managed to do more than 4x the work before our muscle is equally fatigued. But we shouldn't reduce the weight too much. Because to move the weight, we have to move our arms (or our legs if we cycle), but that is a fixed load, the larger the added weight, the smaller its impact. So one problem favours lower load, the other higher load. Between the two is a sweet spot, a load requiring a force that is most efficient. With bicycles we have the added problem that we can only efficiently push on the downward portion of the revolution, roughly 90° of the 360° total. Slight correction to the video here: Pushing down on the pedals is more efficient than pulling up. Pedals that allow you to pull up are great for added control, consistant foot position and it does increase the maximum power you can put into them, so it's great for sprinting or short, but really steep hills. But even professional riders barely use pulling forces outside of moments of peak output, because our muscles for extending the legs (fighting gravity) are just that much better developed than those pulling the leg up. But back to the problem: Two optimal sections of roughly 90° leaves a gap, when one leg becomes inefficient and before the other becomes efficient. That's why it's best to pedal at 60-90 rpm. If you fall significantly below that, you'll have to start pushing into the pedals too early, to keep them turning and finish later, hence work the inefficient sections more. In flat terrain this isn't an issue, just slow down a bit or use lower gears. But if hills get too steep, you can run out of gears. When your lowest gear becomes too high, cycling becomes much less efficient, you'll have to grind instead of pedaling nicely. So that's why you should just start pushing your bike, if you want to be efficient. This problem is aggravated by people generally purchasing over geared bikes. I guess being able to hit a faster top speed, because you can still pedal with your high gear is just more enticing than being able to ride up an even steeper hill efficiently.
So I think those are the most important distinctions: Constant speed being best because of drag increasing exponentially with speed, less cooling when climbing, inefficiency of steep climbs and running out of efficient gears.
okay now explain the physics of how the bike stays upright when you’re riding lol
I just feel bad for the amount of views this has. It's an amazing video :(
It would be great if you do a video about Parkour!
Thankyou.👍
Thanks Jade. :)
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It's the cross product, not multiplication
lol what
Dude there is so much wrong information in this video