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I am a math teacher in Chicago, grading projects that my students put together.
One of those projects dealt with my student and his friends riding their mountain bike over a one block distance. He then calculated the speed of himself and his high school friends.Which brings me to my question, their speeds were 30-38mph which threw up a red flag to me, not believing they could achieve that speed. He mentioned in his project that it was a mountain bike, but even if the block was downhill, could they reach those speeds?
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30mph on a flat road isn’t too difficult for a road bike and a mountain bike with the right gear ratios could probably get pretty close. I sorta doubt these kids were able to get to the upper 30s though unless there was a pretty good slope.
As a point of reference, the world record speed on a mountain bike is just over 100mph on a 45-degree mountain slope. So yeah, if their block has a 45-degree slope they could have hit 38mph no problem 😀
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Top speed that I know of is 34mph down hill on a forest service road. I believe I could of gone faster but my eyes started to water.
Could it of been a measurement error? In my experience (I teach HS chem) this is common among students. I would at least ask them how they got their measurements and if there was any possibility of an error. This will allow them to explain if they did do it legit. Also it will let them know if they did not that they better not try to pull one over on you again.
Second, what are you doing correcting during Christmas break?
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While racing road bikes during sprints at the pro level speeds get up to and over 40 on flat ground.
Kids on mountain bikes, umm might be tough unless its a steep hill and they have some momentum before the starting line.
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I would suggest you check their calculations, first of all, Then maybe have them reperform the test in a parking lot. I am familiar with Chicgo area, I don’t think there are any neighborhoods in northern Il. that would have a Hill steep enough to get a kid on a mountain bike that fast. Much less a group of them. MAYBE in one of those Chicgo winter storms where the 40 MPH winds and they had about a mile and half to build speed. But then I doubt it.
30 to 38 MPH is low level pro racing on a road bike. I have acheived 35 MPH on a flat road on a road bike many times. NEVER have I riden that speed on flat surface on a Mountain bike.
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On dirt the fastest I have sustained is 30-35mph, descending the fire road from Monarch Pass Trail. On the paved Highway 285 portion back down to Poncha Springs I coasted at 47MPH, which remains the "high speed" in my cycling computer to this day.
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I should point out that 47MPH my gears were completely run out on my mountain bike with 44tooth chainring and 11tooth cog.
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A LONG time ago (when mammoths still roamed the tundra and I was 21) my family rode our MTBs across the Denali Highway as a family trip. It is about 133 miles from Cantwell to Paxson Lake Lodge. Most of it is 2-lane, washboard gravel highway, but the last 20 miles into Paxson is paved and comes down out of the Amphitheater Mountains. When my mom leapfrogged me for the last time in the support vehicle, she paced me at between 45 and 50 mph on a long, steep straight-away. The knobbies were buzzing like crazy and I was afraid to pedal OR touch the brakes. When I got to the bottom I just let it run out on to the flat section of highway and let friction slow me down. I bet with hybrid or cross tires someone could squeeze out a few more mph on that stretch, but I wasn’t about to try it!
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"ChiliPepper" wrote
Yeah, I would definitely see how they calculated the distance for sure or at least have them prove it to you directly or recorded on video. Good luck! 😃
Just another thought; if you CAN get video of their run, check with your school’s science department, they may have some data analysis software that allows for data collection straight from the video clip. I am a HS Physics/AP Physics teacher and use the latest version of [i:3lgusq25]LoggerPro[/i:3lgusq25] from [i:3lgusq25]Vernier Software and Technology[/i:3lgusq25]. It definitely could handle that if the camera was set up properly.
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I think we have enough evidence to put these kids away for a long time,hahahahaahaha. 😆
I was doing about 35 down boulder canyon road on my marin pine mtn when my front tire blew out,talk about white knuckles,had to be pretty freindly with the front wheel coming to a stop….
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There are a few flat roads on my way to work, the longest is about 1 mile and seriously pounding the crank arms will get you about 27mph depending on wind resistance, traffic and pot holes.
other than that the bike runs out of road
it could be a mis calibrated spedo or the odd guestimated value throwing the calculations off.
Dac
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Maybe it was 30-38 Kmh instead …. 😏
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I love all of the replies. The students had a radar gun to clock their speed, and it was a city block on Chicago’s Southside, so it sounds like there is no way the hill could have been big enough. I am going to have the student either prove it to me on a flat road, or redo the project!! His math was pretty good on the project, but I think he jus made up those numbers. Thanks again for all of your help, and I love the comment about correcting papers over break.
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off topic but
When i was younger, using my recently retired cruiser when that was younger i simply rolled down a 45 degree hill took about 10 mins but hit 57MPH, stopping at the main road road of the bottom did not happen despite skidding through a tyre and almost parked in the barbers chair opposite (stopped about an inch from the 10 foot sheet glass window), (My friend on a bmx ended up in some ones garden hugging a rose bush(kodak moment))
that was fun, stupid but fun
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The speed seems achievable just not sure about the distance they are claiming to have done it in. I have hit 27 mph on my mountain bike on a flat long road peddling my but off in top gear, and 34 mph on a fairly short downhill road section with plenty of speed before even getting to the downhill section. I might have gone a little faster but the road flattened out.
I don’t doubt they might have hit those speeds but I would have to see some proof of the actual distance they claim to have done this in.
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i put road tire on my bike and ride it to school/work and i can do 31.5MPH on a flat and 43MPH down a hill that is prolly three football fields long, but thats having a lot of momentum going into it too. i also did 55MPH on a flat one time…but that was with a rope tied to a car…
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