# Two similar-looking mechanics questions are not duplicates

This question about which way a bicycle will move when the pedal is pulled horizontally was closed as a duplicate of this question about how a yoyo will move when it is pulled horizontally.

They are not the same question, because a yoyo is a rigid body, while a bicycle is not even close. The correct answer is that in mid gear, the answer is the same as in the yoyo case, but for low gearings the bike will move forward while the pedal moves backward (so the string still ends up going backward as required).

• Voting to reopen. I agree that this isn't the same and shouldn't be closed as such. It's a related question; but I think it's a bit much to say they are identical when the setup is significantly different.
– JMac
Sep 20, 2018 at 19:27
• For an argument that the two questions are the same, consider this video which addresses both. (This isn't me making policy as a moderator; this is me thinking out loud.)
– rob Mod
Sep 20, 2018 at 20:32
• @rob It does explain both, but they're simply not the same question. The bicycle question is more subtle, because the bike may go in either direction. Or, you can think of the yoyo question as a special case of the bike question, the case of $1:1$ gearing. Sep 20, 2018 at 20:42
• If the yo-yo question had been asked later instead of earlier, it would have been correctly closed as a duplicate of the bicycle question: solving the bicycle question gives you a solution to the yo-yo question for free.
– rob Mod
Sep 20, 2018 at 21:26
• I wrote one of the answers to the bicycle problem. In my view, the yoyo problem is essentially a special case of the bicycle problem. As I wrote in my answer, the bicycle can go either forward or backwards depending on whether the bicycle is in high gear (goes backwards) or low gear (goes forward). As drawn, the yoyo is effectively in "high gear" since the diameter of the yoyo's surface holding the string is smaller than the diameter of the yoyo itself, so it goes "backwards" (i.e., towards the direction of the string/rope) just like the bicycle in high gear.
– user93237
Sep 21, 2018 at 4:48
• Not sure why a meta post was made when all of the relevant information could fit into a comment with the reopen vote... Sep 21, 2018 at 11:04