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Merry *ff*ng Christmas

t's the Festive Season, a time for jollity and conundrums.
These may not be too demanding sitting down at home, but may be worth trying on your mates in the cafe after 40 hard miles

1)  It's the Christmas Time Trial. Rider #9 sets off and rides down the road at 20mph. One minute later Rider #10 starts and rides at 30mph. 
How far along the road is it before number 10 catches his minute man?
Assume no time is lost accelerating up to speed.

2)  A man who weighs 14st 4lbs  pumps up both tyres on his bike to 100psi. He then gets on the bike
  What is the pressure in each of his tyres?
Assume his weight is equally distributed between both wheels. The Gatorskin tyre casing is rigid.

3) When you are riding along the road, do your wheels go round and round?
Discuss.

4) You have just finished your training ride and are pottering home for the last couple of miles. 
It starts to rain with big drops falling vertically from the sky. The tumble dryer is broken and you want to stay as dry as possible.
Do you a) Carry on riding slowly? Or b) Ride as fast as you can to get home sooner?
Assume you have perfect mudguards, so no road spray.
 

If you're new please join in and if you have questions pop them below and the forum regulars will answer as best we can.

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16 comments

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Argos74 | 2 years ago
0 likes

3) The wheels on the bike go round and round, round and round, round and round. The wheels on the bike go round and round, all day long.

I hope this is clear.

4) See 3.

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Gimpl | 2 years ago
2 likes

Crikey - a 14st 4lbs person being referred to as a fatty!

That was my 'skinny' weight when I had a 31" waist and a six pack!!

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brooksby replied to Gimpl | 2 years ago
0 likes

Were you, like, eight feet tall?  I'm thirteen stone something, and have a 34-35" waist...  (and no six pack).

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Gimpl replied to brooksby | 2 years ago
2 likes

Funnily enough I'm still about the same height - maybe fractionally shorter thanks to age and the weight of responsibility. yes

6'4" - former second row.

My 18 year old, very skinny, 6'5" son weighs around 13 stone - it's amazing the difference a few inches makes 

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Rendel Harris replied to Gimpl | 2 years ago
1 like

Just shows how weight is completely relative - at the "height" of my playing career as a 6ft back row/utility back I weighed 13 stone 12 lb with a 30 inch waist, certainly had a much more impressive body (this was 20 years+ ago) than I have now I am 12 stone 11lbs!

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Cycloid replied to Lance ꜱtrongarm | 2 years ago
6 likes

F*ck off you thick b*st*rd

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Rendel Harris replied to Lance ꜱtrongarm | 2 years ago
2 likes

Garage at Large wrote:

2) the pressure in the tyres would be 0 psi because the fat guy would insta pop the tyres as he sat down.  

In fact even if the tyres burst because of the weight of the "fat guy" (Maro Itoje weighs 18 stone 2 lbs, I would pay good money to see you calling him a fat guy to his face) the air pressure in the tyres would remain at the ambient pressure of one atmosphere (approximately 14 psi). A pressure of 0 psi would exist only in a perfect vacuum.

Garage at Large wrote:

3) Yes. Either that or the wheels stay still and the entire planet is orbiting the bike, take your pick.

What you actually mean is if the wheels stay still whilst the planet rotates underneath them, not orbits the bike, which would require the bike to be suspended in space.

You certainly are not the smartest person on road.cc, though I will accept your claim to be on about the same intellectual level as the former President. 

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mdavidford replied to Lance ꜱtrongarm | 2 years ago
4 likes

Garage at Large wrote:

In any case who mentioned the man was on planet Earth?

It's a fair point, given that the person answering the questions doesn't spend any time there.

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AlsoSomniloquism replied to mdavidford | 2 years ago
5 likes

Well being as Cycloid mentioned doing this with cycling mates at the cafe stop......you can see why Boo doesn't know how to behave around them.

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Cycloid | 2 years ago
1 like

Two observations
Wrong answers are always better than the right ones - keep 'em coming.
You can't have a sensible conversation with your cycling mates in the cafe - they are too busy taking the p*ss (which is a good thing)
 

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Tom_77 | 2 years ago
1 like

1. 1 mile

2. 100 psi

3. No, the world revolves around me

4. As fast as possible, although it makes very little difference - https://www.sciencefocus.com/planet-earth/do-you-get-wetter-if-you-run-o...

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Cycloid replied to Tom_77 | 2 years ago
0 likes

Good reply

Check out the Cycloid curve for question #3

Thanks for the link for question #4, I'll follow it through
I was expecting the answer to involve some 'orrible differential equations.

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hawkinspeter | 2 years ago
6 likes

1) Let's see - after 1 minute, #9 has cycled 1/3 mile and #10 has cycled 0 miles. But by the time #10 has cycled 1/3 mile, #9 has also cycled a bit further. So no matter how many times #10 cycles the same distance, #9 is always a bit further ahead. Therefore it is impossible for #10 to ever catch #9.

2) With a bit of finite element analysis, we can determine that the rider and bike are being supported merely by the pressure in the tyres and the rigidity of the Gatorskins. As the casing is assumed to be perfectly rigid, this means that the air pressure is not supporting any weight at all. Thus, we can prove that the tyres are merely subject to social pressure to perform well as tyres.

3) By examining the contact point between the road and the tyre, it's clear that the tyre is static at that point (unless you're performing some wicked skids) and so obviously, the entire wheel must be static too as it is a rigid structure.

4) I'll take option b) please. Imagine if you will, the trajectory of a raindrop falling vertically onto my head. If I then move forwards, the raindrop will surely fall behind me as long as I am moving quickly enough for the time taken for the raindrop to fall is longer than the depth of my head. This means that I can remain completely dry unless the clouds are low - this also explains why misty rain is a lot wetter than ordinary rain as the clouds are lower.

 

TheBillder wrote:

*Supplementary question: what's the smallest pet in the world?

I keep a small proton as a pet - it helps me stay positive.

For bonus points - see if you can connect the dots in this picture:

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TheBillder replied to hawkinspeter | 2 years ago
2 likes
hawkinspeter wrote:

TheBillder wrote:

*Supplementary question: what's the smallest pet in the world?

I keep a small proton as a pet - it helps me stay positive.

It's my newt.

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mdavidford | 2 years ago
10 likes

1. He doesn't. TTs are so phenomenally dangerous that the whole thing is called off due to it causing a massive accident before he has the opportunity.

2. Trick question. He's a fatty, so he would be riding large tyres at lower pressures.

3. Only so long as there isn't a Very Important Driver who requires me to pull over out of their way.

4. c) I ride slowly and cautiously and pull over and stop every time I encounter a Very Important Driver, cheerfully accepting the drenching as they speed through the puddles with a courteous wave in response.

[I may have collaborated with another regular poster on my answers - I hope that's OK?]

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TheBillder | 2 years ago
8 likes

1) You didn't mention that no 10 had a diminutive friend in the race so we can't tell*

2) If latex tubes, atmospheric pressure only. If tubeless, we won't know until next week as they still haven't seated. If butyl, it's winter so we need to know where the thorns have been inserted.

3) No, it's the wheels on the bus that do that. Were you not concentrating at nursery? Don't they teach them anything nowadays?

4) Neither. You call nic mason to drive you home and you get there before the third drop has fallen, as there is no need to adjust speed or course for mini roundabouts or speed bumps.

Have I won?

*Supplementary question: what's the smallest pet in the world?

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