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Steve Robson

Marine Industry

Learning and Development Consultant

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Bicycle Problem?


Thanks to Shirley from Azesta for sharing this...

Does the bike go Forwards, Backwards or Stay in the Same Place?

25 Responses

  1. Clarification

     How long is the string, and how much am I pulling it?

    Is the bicycle supported?

  2. To Clarify

    This is not a trick btw…

    Bicycle is supported but not restrained…string is 1 metre…you can pull for as long as you want.

  3. Easy!

    OK, I know the answer, but will leave it open for other people to get involved first (will send you a personal message so you know I’m not cheating)

  4. Oops

     Haha! I’ll have to disagree and go off in a huff saying "no, YOU’RE wrong!"

  5. Bike and String

    Go get your bike and a bit of string like I did… its magic ūüėČ

  6. Not likely

     It’s downstairs as we speak, but as it’s my "expensive" bike I don’t fancy someone dropping it as I try it!

  7. it wouldn’t move because…….

    ….there is no such thing as a "peddle" on a bike, it has two "pedals", but "peddle" is a verb meaning ‘to sell’….

    …or wasn’t this a QI-Klaxon-invoking question for a Friday afternoon?

    Rus Slater

  8. a guess….

    stays in the same place?

    "to every action there is an equal and opposite reaction"


  9. no….

    there is so much stuff in the garage that I can’t reach my bicycle!

  10. ha

    Oh dear…weekend cleaning out the garage?

    There is a moral to this question that will be revealed on Monday!

  11. Who moved my cheese, sorry, bike

    Now as nobody has given the answer (publically) I’m not sure I should either. But here goes…

    As it is a man’s bike, it is ultimately destined to go backwards. Only a man would be stupid enough to tie string to a pedal and use that as a means of propulsion. However, having done so, said man is bound to pull and pull until the bike hurtles towards him and causes serious injury. Or at least that is what happened to me when I tried it. This is a site about learning and I have now learnt my lesson.

    Had the bike been a penny farthing, with no gears, the bike would have gone forward a little. In fact had you got it going with the right momentum and pulled at the right time, you could keep it going forward. If you look at how the wheels work on a steam train you will get the general idea. It is a little known fact that Stephenson used this very experiment before inventing the rocket. Being a genius he realised quite quickly that bikes and string had no future and so shifted his focus to a kettle on wheels.

    But it is the standing still option that most appeals. Setting up such a creative exercise to simply end up going nowhere could only be the work of a trainer. The real art is then in extracting the learning we can take back to the workplace. In this case it is all about being able to conceptualise a problem and forecast likely outcomes. A good trainer can always peddle a learning point.

    Is there a prize?



  12. Every which way but loose

     Hey ho! I clearly need to expand on my earlier answer.

    If you pull hard enough the bike will move in the direction of the pull: backwards. If the bike is of fixed wheel design or is geared, and the pull is a short one, the pedal will drive it forward (to keep it going forward see the technique I describe above). If the bike is able to free-wheel in both directions, as happens with a Shimano 6208 Freewheel, and the pull is short, then then the pedal turns and the bike goes nowhere.

    The answer is that it depends.

    Furthermore, the options you give are somewhat limited. If the string is on the inside of the pedal and the rear brake is on hard, then the bike is likely to lift and go upwards. If the string is on the outside of the pedal then it will go right, or at least the front end will. If you apply any of these techniques the bike will at some stage fall over: and so travel downwards. These options all derive from deductive reasoning.

    So how about a challenge that involves a little more lateral thinking. How can you make the bike go left when you pull the string? I have thought of three solutions and will happily share them…later (just in case anyone wants to use this thinking exercise on a problem solving course, and in the vain hope that it might get me my prize. I do so want a prize!).

    In the meantime, any offers of a solution?


  13. Newton’s Law


    Now this thread is off the front page of Any Answers I guess it will get less traffic. I’m assuming the ‘correct’ answer – along with all those I posted above – is that the bike, initially, goes nowhere. The forward force from the pedal is equal and opposite to the rearward force of pulling the string, as stated by Russ.

    But making it go left, that is your challenge if you wish to take it up.


  14. 3 choices
    Really good answer Graham. However you only had 3 choices and every answer you give is not one of the choices. only 1 answer allowed and you have to be 100% sure. Fwd Bwd Still. Take your pick.

  15. All three

    Firstly, it depends upon two things: 1. surface you have your bike on. 2. the design of the freewheel mechanicsm you have on the backwheel.

    However, assuming it’s a relatively normal concrete surface and a standard freewheel which allows the back wheel to rotate freely so that the bike can move forward without the pedals rotating, but backwards whilst rotating the pedals, the following is proven by experiment:

    If it is in a high gear (used for going fast) the bike will move backwards, as the backwards force provided by the pull on the string will outweigh the amount of rotational force applied to the back wheel (it’s REALLY hard to get going forward if you’re in a high gear and essentially the pedal will remain in a fairly fixed position relative to the bicycle).

    If it is in a low gear (used for climbing steep hills), it will move forwards, as the rotational force required to rotate the back wheel is much less due to the gearing, however it will only go forward for a very short amount – about half the length of the crank arm before moving backwards again as the forces equal out and tip over in favour of the string.

    What I found most interesting is if it’s in just the right gear and the pull on the string is relatively even (not tugging or increasing in force), the two forces will balance out and the bike will remain still.

    Try it, it’s fun finding the right gear to make it still!

    Now I have to go untangle string from my bike.


  16. 1 word

    Thanks for the detailed explanation Mazza. Was a bit more than I was looking for but you did prove my point…

    Which is…

    How did you find out the answer?

  17. Taking a bike to water and hoping it drinks

     At the serious risk overkill, I’d like to make some broader points.

    Firstly, and possibly surprisingly, this wee challenge, Steve, could be one of the most important questions ever asked on Any Answers.

    It is all about thinking skills. I know you have intimated that trying it out is the best way to solve this little puzzle, and actions are the best test of ideas. But this deceptively innocent exercise reveals some deeper truths about one of the most critical skills in today’s world. The ability to think through options, solutions and potential consequences is every bit as crucial as learning any behavioural skill.

    One only has to recall the flawed thinking behind Marconi’s over-ambitious strategy and their consequent demise to realise how important it is to be able to combine imaginative and holistic ideas with practical and grounded rational thought. If one cannot think through the consequences of pulling a bit of string, what hope is there for developing complex plans in a highly volatile environment.

    And yet we probably invest 10 times as much time time, money and effort into developing people’s behavioural skills as we do in building their thinking capabilities. A challenge such as the one you posed could be used to help explore some of these skills. Firstly, I’m sure some people found a seemingly trivial question a turn off. These are the very people who might most benefit from exercising their intellectual muscles in a new direction.

    Secondly, there are various logical ploys one can play with. There is the capacity to anticipate, to challenge one’s first perceptions, to determine the conditional factors, to model or try out one’s theories in one’s head before going live. There is also scope for lateral thinking and, as with the Kobayashi Maru scenario, to change the rules. 

    Yes, you have offered up a fun little game. But if you are willing to entertain bigger thoughts, it is also a lesson to us all that thinking is a fundemental skill, and one that we can always develop further. Had Marconi had such an exercise in their management training, maybe they would still be around today.

    That is probably enough of pontificating for now!

    On the additional challenge I set, about getting the bike to go left, there are many answers. You can point the bike south and let the earth’s rotation do the rest. You can hold the string taught and then jerk it to the left. Or, my favourite, you can look at the screen and imagine pulling the string gently with your left hand. An then with your right hand, equally gently, push the screen away from you.

    Creativity lives!


  18. Best Answer

    Graeme…you took the words right out of my mouth. Unfortunately "Best Answer" has gone.

    I did actually steal" the bicycle question" from a course I was on so can’t claim credit but thought it was so poweful I shared it on here. Not often I’m blown away anymore but this simple little question is pretty amazing!

    I have another and this time its all mine…watch this space…(Or any answers)

  19. thinking…

    Usually scientifically. Guess (hypothesise), design an experiment to prove or disprive (already done for me here), try it.

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Steve Robson

Learning and Development Consultant

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